refactor(coding-agent): narrowed over-exported internal symbols

- 28 symbols across discovery, mcp header policy, agent-hub projection and
  rendering, the agent registry, shell tokenizing and changelog comparison
  were exported but referenced only inside their own module; they are now
  module-private, shrinking the deep-import surface.
- Kept AGENT_PLUGIN_MANIFEST_SCHEMA, AGENT_PLUGIN_MCP_SCHEMA,
  parseAgentPluginManifest, clearAgentPluginRootCache and mergeMCPHeaders
  exported: each is a seam for tests that defend real parsing or header
  precedence behavior.
- Nothing reachable from an explicit exports entry or public barrel changed.

packages/coding-agent/src/discovery/agent-plugin-format.ts

@@ -74,13 +74,13 @@ export interface AgentPluginManifest {
  * - `invalid` — the document targets Agent Plugins but violates the closed schema
  *   fatally; the plugin must be rejected and none of its components loaded (spec §5.2).
  */
-export type AgentPluginManifestResult =
+type AgentPluginManifestResult =
 	| { status: "none" }
 	| { status: "valid"; manifest: AgentPluginManifest; warnings: string[] }
 	| { status: "invalid"; reason: string };
 
 /** Enforce the plugin `name` constraints from spec §5.5. */
-export function isValidAgentPluginName(name: string): boolean {
+function isValidAgentPluginName(name: string): boolean {
 	if (name.length < 1 || name.length > 64) return false;
 	if (!/^[a-z0-9](?:[a-z0-9.-]*[a-z0-9])?$/.test(name)) return false;
 	return !name.includes("--") && !name.includes("..");
@@ -240,14 +240,14 @@ export function parseAgentPluginManifest(raw: string): AgentPluginManifestResult
  * (spec §9.2). Single non-recursive pass; replacement text is never rescanned,
  * and no other placeholder or environment-variable expansion is performed.
  */
-export function expandAgentPluginPlaceholders(value: string, pluginRoot: string, pluginData: string): string {
+function expandAgentPluginPlaceholders(value: string, pluginRoot: string, pluginData: string): string {
 	return value.replace(/\$\{PLUGIN_(ROOT|DATA)\}/g, (_match, which: string) =>
 		which === "ROOT" ? pluginRoot : pluginData,
 	);
 }
 
 /** A validated `mcp.json` server entry, resolved to launch-ready values. */
-export interface AgentPluginMcpServer {
+interface AgentPluginMcpServer {
 	name: string;
 	transport: "stdio" | "http" | "sse";
 	/** Absolute path for `./`-relative commands; bare executable token otherwise. */
@@ -268,11 +268,11 @@ export interface AgentPluginMcpServer {
  * - `ok` — the document is valid; individually invalid server entries are
  *   skipped with a warning (spec §7.2.2 rule 3).
  */
-export type AgentPluginMcpResult =
+type AgentPluginMcpResult =
 	| { status: "disabled"; reason: string }
 	| { status: "ok"; servers: AgentPluginMcpServer[]; warnings: string[] };
 
-export interface AgentPluginMcpOptions {
+interface AgentPluginMcpOptions {
 	/** Filesystem-resolved plugin root. */
 	pluginRoot: string;
 	/** Client-managed persistent data directory for this plugin (spec §9.1). */
@@ -488,7 +488,7 @@ export async function parseAgentPluginMcp(raw: string, options: AgentPluginMcpOp
  * - `invalid` — the root claims Agent Plugins conformance but its manifest is
  *   fatally invalid; no component may be discovered or executed (spec §11.3).
  */
-export type AgentPluginRootStatus =
+type AgentPluginRootStatus =
 	| { kind: "none" }
 	| { kind: "standard"; manifest: AgentPluginManifest; warnings: string[]; realRoot: string }
 	| { kind: "invalid"; reason: string };

packages/coding-agent/src/discovery/contained-path.ts

@@ -14,7 +14,7 @@ import * as fs from "node:fs";
 import * as path from "node:path";
 
 /** Lexical containment: `target` is `base` itself or a descendant of it. */
-export function isContained(base: string, target: string): boolean {
+function isContained(base: string, target: string): boolean {
 	const relative = path.relative(base, target);
 	return relative === "" || (!relative.startsWith("..") && !path.isAbsolute(relative));
 }
@@ -29,10 +29,7 @@ export async function realpathIfExists(p: string): Promise<string | null> {
 }
 
 /** Outcome of resolving a fixed package path without reading it. */
-export type ContainedPathResolution =
-	| { status: "missing" }
-	| { status: "outside" }
-	| { status: "ok"; realPath: string };
+type ContainedPathResolution = { status: "missing" } | { status: "outside" } | { status: "ok"; realPath: string };
 
 /**
  * Resolve a fixed package path WITHOUT reading it: symlinks and equivalent

packages/coding-agent/src/mcp/transports/header-policy.ts

@@ -14,7 +14,7 @@
  */
 
 /** Header buckets for one MCP HTTP request. */
-export interface MCPHeaderSources {
+interface MCPHeaderSources {
 	/** Client-generated HTTP/MCP/authorization headers; win case-insensitively. */
 	generated: Record<string, string>;
 	/** Configured headers from the server entry (package or user config). */

packages/coding-agent/src/modes/components/agent-hub-projection.ts

@@ -10,7 +10,7 @@ export interface AggregateMetrics extends AgentMetrics {
 	activeDurationAgents: number;
 }
 
-export interface AgentTreeProjection {
+interface AgentTreeProjection {
 	rows: AgentRef[];
 	depthById: Map<string, number>;
 	parentById: Map<string, string>;
@@ -65,7 +65,7 @@ export function progressMetrics(observed: ObservableSession | undefined): AgentM
  * usage embedded in completed `task` tool results, so using it for a parent
  * row would double-count child rows in the aggregate.
  */
-export function readSessionMetrics(session: NonNullable<AgentRef["session"]>): AgentMetrics | undefined {
+function readSessionMetrics(session: NonNullable<AgentRef["session"]>): AgentMetrics | undefined {
 	try {
 		const stats = session.getSessionStats();
 		const messages = session.agent?.state?.messages;

packages/coding-agent/src/modes/components/agent-hub-renderer.ts

@@ -16,7 +16,7 @@ export interface RosterRender {
 }
 
 /** Legacy progress snapshots may omit counters; snapshot absence remains distinct. */
-export function metricNumber(value: number | undefined): number {
+function metricNumber(value: number | undefined): number {
 	return typeof value === "number" && Number.isFinite(value) ? value : 0;
 }
 
@@ -67,7 +67,7 @@ export function statusText(status: AgentRef["status"], text: string): string {
 }
 
 /** Model id + thinking level (`sonnet-4-6 ◒ high`), level colored per theme. */
-export function formatModelBadge(modelId: string, level: ThinkingLevel | undefined): string {
+function formatModelBadge(modelId: string, level: ThinkingLevel | undefined): string {
 	const model = theme.fg("muted", sanitizeDisplayText(modelId));
 	if (!level || level === ThinkingLevel.Off || level === ThinkingLevel.Inherit) return model;
 	const display = theme.thinking[level as keyof typeof theme.thinking] ?? level;
@@ -81,11 +81,7 @@ export function formatRoleBadge(role: string, settings: Settings): string {
 }
 
 /** Format a resolved selector, preserving provider identity when requested. */
-export function formatResolvedModelBadge(
-	resolved: string,
-	preserveProvider = false,
-	fallbackLevel?: ThinkingLevel,
-): string {
+function formatResolvedModelBadge(resolved: string, preserveProvider = false, fallbackLevel?: ThinkingLevel): string {
 	const cleanResolved = sanitizeDisplayText(resolved);
 	// Model ids may themselves contain colons (`qwen3:14b`), so only treat the
 	// suffix as a thinking level when it parses as one.

packages/coding-agent/src/registry/agent-registry.ts

@@ -15,7 +15,7 @@ import { oneLineLabel } from "../task/types";
 export const MAIN_AGENT_ID = "Main";
 
 /** Sidecar marker retained beside a child transcript after an explicit kill. */
-export const AGENT_TOMBSTONE_SUFFIX = ".tombstone";
+const AGENT_TOMBSTONE_SUFFIX = ".tombstone";
 
 export function getAgentTombstonePath(sessionFile: string): string {
 	return `${sessionFile}${AGENT_TOMBSTONE_SUFFIX}`;
@@ -30,7 +30,7 @@ export function getAgentTombstonePath(sessionFile: string): string {
  */
 export type AgentStatus = "running" | "idle" | "parked" | "aborted";
 /** Provenance of a displayed duration: active runtime, transcript span, or unavailable. */
-export type AgentDurationKind = "active" | "span" | "unknown";
+type AgentDurationKind = "active" | "span" | "unknown";
 /**
  * - `main`/`sub`: the user-facing agent tree (driving agent + task subagents).
  * - `advisor`: a passive review transcript persisted like a subagent for usage

packages/coding-agent/src/tools/shell-tokenize.ts

@@ -87,7 +87,7 @@ export function tokenizeShellSegments(command: string): string[][] {
  *
  * @see extractFlatShellCommandSegments
  */
-export interface FlatShellCommandSegment {
+interface FlatShellCommandSegment {
 	/** Original segment text with quoting and escaping preserved. */
 	text: string;
 	/**

packages/coding-agent/src/utils/changelog.ts

@@ -201,7 +201,7 @@ function parseChangelogContent(content: string): ChangelogEntry[] {
  * Compare changelog entries by their parsed version parts.
  * Returns: -1 if v1 < v2, 0 if v1 === v2, 1 if v1 > v2
  */
-export function compareChangelogEntries(v1: ChangelogEntry, v2: ChangelogEntry): number {
+function compareChangelogEntries(v1: ChangelogEntry, v2: ChangelogEntry): number {
 	if (v1.major !== v2.major) return v1.major - v2.major;
 	if (v1.minor !== v2.minor) return v1.minor - v2.minor;
 	return v1.patch - v2.patch;