[bryantderosier]

What Changed

Adds a shared @agent:<id> picker for Codex and Claude. Saved agents run as subagents under the current conversation with their own immutable instructions, model route, reasoning, and runtime policy. Completion returns to the parent; crews remain out of scope.

The web/desktop and mobile composers reuse their existing menus. J5 modules own lookup and invocation; FORK.md records the small upstream integration hooks.

Why

Imported agents could be managed in Settings but could not be invoked consistently from prompts. The new picker connects the saved definitions to the existing child lifecycle without changing provider adapters or adding a second task engine.

Validation

• 131 focused invocation, composer, contract-boundary, and MCP registration tests pass across 14 files.
• Server, web, and client-runtime typechecks pass. Mobile has 62 existing navigation type errors, identical to the base comparison.
• Browser verification confirms agent suggestions and identical editable mention syntax in Codex and Claude. Backend integration verifies one nested child, saved assignment, and retry idempotency.
• Live provider completion remains unverified: Claude was signed out and the isolated Codex environment failed its CLI identity check.
• git diff --check passes.

UI Changes

Before/after screenshots were captured locally. Upload is deferred at Bryant’s request; no PR-only images are committed.

Checklist

• Changes implement saved-agent invocation with focused commits
• Behavior and fork boundaries are documented
• Focused tests and scoped typechecks completed
• Before/after evidence uploaded (deferred at Bryant’s request)

Merge order

This PR extends GitHub stack pingdotgg#120 and depends on #85. Merge bottom to top:

#75 → #76 → #78 → #79 → #80 → #81 → #83 → #82 → #85 → #118

The Claude sign-in verification that briefly lived here was reverted on 2026-09-09; Bryant is upstreaming it to pingdotgg/t3code separately.

Stack rebuilt 2026-09-09 (stack pingdotgg#120): #84 and #86 were dropped, and fork-boundary refactors moved the persona RPCs, guards, and client wiring into J5-owned files. Review threads were preserved.

Implemented with GPT-6 using the Codex desktop app.

Also on 2026-09-10 (roadmap items 3 and 6): new-task drafts on web and mobile offer an Agent control that starts the task as a saved agent (the launch carries the agent request; the server pins the route), and agent identity now shows on thread rows in both thread lists and on delegated children in the Agents panel. Draft selection is session-local J5 state; upstream composers gain one hook call and two mounts each, recorded in FORK.md.

Rebased on 2026-09-10 onto #85's usage, library sources, and copy-to-environment work. The same push fixes the one failing web unit test on this branch: the identity label gained min-w-0 for flex truncation and ThreadCardIdentity.test.tsx still asserted the old class string.

Stack rebased onto j5/main at 4f95ee26b on 2026-09-11 after #109 landed. The only conflict was the sorted MCP tool list in registration.test.ts, where this PR adds invoke_agent and #109 adds list_artifacts; both are kept.