fix(coding-agent): identify user-invoked skills and expose skill directory

User-invoked skills (typed /skill:, steered, follow-up, interrupted/
resumed via compaction, ACP, RPC) only appended a bare "Skill: <path>"
line, so the model neither learned the user had invoked that specific
skill nor where the skill directory was. Relative paths in skill bodies
(scripts/, templates/) could not be resolved.

Route all user-invoked paths through a self-identifying, baseDir-aware
prompt template; keep hidden autoload skills on the minimal non-user
format. Interactive skillCommands now carries the loaded Skill object
instead of a bare path so baseDir flows through without reconstruction.
The invocation kind defaults to "user" to keep buildSkillPromptMessage
source-compatible.

Op: correct
Restores: spec:user-invoked-skill-prompt-self-identifies-and-exposes-skill-directory

packages/coding-agent/src/modes/interactive-mode.ts

@@ -65,6 +65,7 @@ import type {
 	ExtensionWidgetOptions,
 } from "../extensibility/extensions";
 import type { CompactOptions } from "../extensibility/extensions/types";
+import type { Skill } from "../extensibility/skills";
 import { loadSlashCommands } from "../extensibility/slash-commands";
 import { type GuidedGoalMessage, runGuidedGoalTurn } from "../goals/guided-setup";
 import type { Goal, GoalModeState } from "../goals/state";
@@ -478,7 +479,7 @@ export class InteractiveMode implements InteractiveModeContext {
 	lastStatusSpacer: Spacer | undefined = undefined;
 	lastStatusText: Text | undefined = undefined;
 	fileSlashCommands: Set<string> = new Set();
-	skillCommands: Map<string, string> = new Map();
+	skillCommands: Map<string, Skill> = new Map();
 	oauthManualInput: OAuthManualInputManager = new OAuthManualInputManager();
 	collabHost?: CollabHost;
 	collabGuest?: CollabGuestLink;
@@ -687,7 +688,7 @@ export class InteractiveMode implements InteractiveModeContext {
 		if (settings.get("skills.enableSkillCommands")) {
 			for (const skill of this.session.skills) {
 				const commandName = `skill:${skill.name}`;
-				this.skillCommands.set(commandName, skill.filePath);
+				this.skillCommands.set(commandName, skill);
 				skillCommandList.push({ name: commandName, description: skill.description });
 			}
 		}