docs: added auth-broker, schema-normalize, install-id, and eval docs

- Added auth-broker-gateway.md covering remote OAuth vault, gateway forward-proxy, usage cache layering, and env surface.
- Added ai-schema-normalize.md documenting the unified tool-schema normalization pipeline and strict-mode edge cases.
- Added install-id.md describing the per-install UUID persistence and consumer contract.
- Rewrote eval.md to reflect structured JSON cells schema, removing the legacy `*** Cell` parser and Lark grammar.
- Updated environment-variables.md, models.md, sdk.md, secrets.md, lsp.md, session-tree-plan.md, ttsr-injection-lifecycle.md, and natives docs to match code changes.

docs/tools/lsp.md

@@ -310,4 +310,5 @@ Same as `definition`, but sends `textDocument/implementation` and reports `imple
 - `reload` does not recreate a client immediately after killing it; the next request triggers reinitialization.
 - `workspace/applyEdit` can apply edits initiated by the server outside the direct tool action result path.
 - `detectLspmux()` can be disabled with `PI_DISABLE_LSPMUX=1`; only `rust-analyzer` is in `DEFAULT_SUPPORTED_SERVERS`.
+- Startup LSP warmup (`discoverStartupLspServers(cwd)` in `sdk.ts`) is gated on `enableLsp && options.hasUI && settings.get("lsp.diagnosticsOnWrite")` — print/RPC/ACP/script sessions skip it and let `getOrCreateClient()` cold-start servers on demand. See `docs/sdk.md` § Startup performance.
 - `configCache` is per-process and never auto-invalidated; config changes require a fresh process to be observed by `getConfig()` callers.