feat(coding-agent): auto-generate session title via /rename

[MikeeI]

Summary

/rename now accepts an optional argument. When called without one, it auto-generates a session title using the smol model (commit/smol role) based on recent conversation context. Manual /rename <title> continues to work as before.

Related: #658, #680

How it works

1. /rename builds a compact context summary from the session:
   • Last 5 user + assistant (first line) message pairs
   • Deduplicated tool names used in the session
   • Compaction shortSummary if available
   • Project name (cwd basename)
2. Sends the summary to the smol model via completeSimple with a unified Handlebars prompt
3. Sets the generated title with source: "auto" — no accent coloring, no auto-title lock
4. Manual /rename <title> sets source: "user" as before

Changes

File	Change
title-system.md	Unified Handlebars prompt with {{currentTitle}} and {{projectName}} template vars
title-generator.ts	Extracted shared callTitleModel() helper; added regenerateSessionTitle() accepting a context summary string; cleanTitle() strips # heading markers
command-controller.ts	/rename without arg builds context summary, shows loading spinner, generates title; same-title guard prevents unnecessary updates; extractMessageText() helper for content extraction
builtin-registry.ts	/rename hint changed to [title] (optional); handler delegates to controller for both modes
types.ts / interactive-mode.ts	handleRenameCommand(title?: string) signature
CHANGELOG.md	Documented under [Unreleased]

Design decisions

• source: "auto" for generated titles — no accent color, auto-title not locked. User can always override with /rename <title> (source: "user").
• Assistant first-line only — full assistant messages are too verbose for title context. First non-heading line captures the response summary without token waste.
• No per-message truncation — smol models have large context windows and we send maxTokens: 30 output. The context cost is negligible.
• Compaction-aware — after compaction, messages may be sparse. The shortSummary from the last compaction entry fills the gap.
• Same-title guard — if the generated title matches the current one (case-insensitive), shows "Title unchanged" instead of a redundant update.

---

• bun check passes (pre-existing ajv version mismatch in validation.ts is unrelated)
• Tested locally
• CHANGELOG updated

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 034e4f786c

ℹ️ About Codex in GitHub

Codex has been enabled to automatically review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

When you sign up for Codex through ChatGPT, Codex can also answer questions or update the PR, like "@codex address that feedback".

[chatgpt-codex-connector]

Distinguish locked auto-title from empty title

This branch treats any setSessionName() failure as an empty title, but SessionManager.setSessionName also returns false when source === "auto" and the current title was set by the user. Because /rename without args now always uses source: "auto", a user who previously ran /rename <title> cannot regenerate a title with /rename; they get the misleading Session name cannot be empty. error instead. Handle the user-locked case explicitly (or treat this user-invoked regeneration as a user-source rename) so the command behaves correctly.

Useful? React with 👍 / 👎.

[MikeeI]

Autofix?