Agents can discover connected local Ace windows with `ace tabs --json` and rename one tab with `ace tab rename <window> <channel> <tab> <name>`. Each request targets explicit IDs, rejects stale or closed targets, and waits for the selected window to render and save the name. Empty names restore the default; the Chat tab follows the channel name. These operations require the owner's authenticated loopback connection.

Closes #43. Refs #5. This PR is based on `feat/github-cache` to isolate the tab API from the earlier work on that branch.

Validation passed: workspace type checks, formatting/lint (zero warnings), app build, and real source-runtime checks with two browser windows. Verified unchanged selection, live window isolation, trimming/reset, reload persistence, channel switching, closed tabs/windows, dashboard cleanup, and host restart recovery. A real Anthropic Ace agent discovered the intended window, renamed its terminal through the shell tool, and read back both windows. Authentication and invalid-target checks passed, including real Tailscale browser and peer connections authenticated as the host owner being denied local tab access.

React Doctor reported one performance warning for `flushSync`. The synchronous update is intentional so the acknowledgment contains committed and persisted state; the app currently uses no View Transitions. No warnings were suppressed.

Tab names retain the existing browser-profile layout storage. Competing windows can overwrite each other's saved layout even though live renames target one window; the limitation is documented and tracked in #45. Dogfooding also found collapsed sidebar controls exposed to accessibility navigation, filed separately as #44. No durable channel format changes.

### Built in Ace

Ace Canary's terminal ran dependency installation, repository checks, temporary real-runtime smoke scripts, Git mutations, and GitHub writes. Validation also used the source Ace app and a real Ace agent's shell tool.

Codex coordinated the work, edited and inspected source, and performed read-only repository/GitHub review outside Ace because external harness integration (#9) and a File tab/editor (#22) are still missing. Codex computer-use tools operated the native Ace terminal and inspected the source UI because Ace does not yet expose native UI inspection/control (#8).