/relaunch command - part c

[M-Maciej]

Closes #5532

Summary

/update installs a new binary and then tells the user to restart the app.
This adds the missing self-relaunch so a session switches to the current
binary in one step:

• /relaunch behaves like /exit for persistence (save, restore terminal,
  telemetry flush, session_end emission) and then self-execs
  resume <session-id> — the CLI's positional resume form, which the
  standalone TUI binary also accepts. Atomic exec on Unix: no orphan
  process for a supervisor to reap.
• argv[0] fallback: when current_exe resolves to a deleted or renamed
  path — the updater's rename-replacement case — /relaunch falls back to
  argv[0] instead of failing.
• If the replacement fails, the session is already saved; the error names the
  exact resume command to continue with.
• Windows keeps the documented manual-restart behavior (no exec); the
  portable argv-construction tests still exercise the resume-form builder on
  every platform.

Merge-order note

Merge order: after the cadence fix (a). No dependency on (b); the control
socket's relaunch verb (d) dispatches /relaunch through the generic
command seam, so it has no compile dependency on this branch — until this
merges the verb reports command_error, after it the verb is functional.

Windows build hygiene

The Windows CI gate denies dead code under -D warnings. relaunch_argv is
only called from the unix-only self-exec path, so the plain Windows lib build
flagged it. It is gated with #[cfg(any(unix, test))] — the item itself is
omitted from the plain Windows lib build instead of being allowed — so the
dead-code budget is untouched.

Testing

<!-- Exact gate commands (including the clippy allow list) are in
CONTRIBUTING.md → "Pre-push verification". -->

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features --locked (warning-free under the CI allow list)
• cargo test --workspace --all-features --locked

Results: clippy clean on stable 1.98.0 under the CONTRIBUTING.md allow
list; full suite 13,376 passed / 0 failed (same one pre-existing
environmental skip as the outbox PR). Focused relaunch suite: 12/12
(argv construction incl. Windows-style path preservation,
deleted/renamed-current_exe fallback, resume-form args).

Checklist

• Updated docs or comments as needed — Unreleased changelog entry;
  /update's module doc now explains why it does not chain /relaunch
• Added or updated tests where relevant
• Verified TUI behavior manually if UI changes — /relaunch exercised
  live on running sessions during development ( verified before split, not after )
• Harvested/co-authored credit uses a GitHub numeric noreply address —
  every commit is authored under
  130112810+M-Maciej@users.noreply.github.com
• Every commit carries a Signed-off-by (DCO)
• No dead-code-budget change

[github-actions]

Thanks @M-Maciej for taking the time to contribute.

This repository is observing a maintainer-managed PR intake gate in dry-run mode, so this pull request is staying open. This note helps maintainers prepare the allowlist before any enforcement is considered.

Please read CONTRIBUTING.md for the expected contribution shape. A maintainer can grant recurring PR access by commenting /lgtm on a pull request.

[Hmbown]

Reviewed from the 0.9.12 integration lane: same disposition as #5592 — implements #5532 (unlabeled for v0.9.12 in #5573), standalone off main, so not folded mid-cycle; @Hmbown's call whether 0.9.12 includes /relaunch. Nothing blocking from the description; will take + full-matrix verify on request.

[Hmbown]

Hi @M-Maciej — maintainer housekeeping on this PR, no code of yours was touched.

What I found. Two separate things were keeping this un-judgeable:

1. The merge conflict was trivial. I merged origin/main in and the only conflict was CHANGELOG.md + its generated slice crates/tui/CHANGELOG.md: main's ## [Unreleased] / ### Added list grew while your bullet landed at the same insertion point. Every source file — including crates/tui/src/tui/ui/event_loop.rs, crates/tui/src/lib.rs, crates/tui/src/tui/ui.rs — auto-merged cleanly. I resolved it as "keep both" (main's list with your bullet appended) and regenerated the slice with scripts/sync-changelog.sh. cargo check --workspace --all-targets passes on the result.

2. CI had never actually run on this PR. Not once. The repo is set to approval_policy: first_time_contributors for fork PRs, so your pull_request workflows were withheld pending a maintainer click — and nobody was watching that queue. The only two green checks you were seeing (gate, GitGuardian) are the two paths exempt from that gate. That is our process failure, not anything you did. Pushing the merge commit as a maintainer released the gate, so the full matrix is running on this PR right now for the first time.

I also prepended Closes #5532 to the PR description — the required link check wants an explicit closing keyword, and your commits already pointed at that issue.

Heads-up on what CI will report. main is currently red on two required checks that every open PR inherits, so ignore these if you see them:

• Version drift — main is missing a changelog receipt for feat(tui): make Fleet roster editing discoverable #5604.
• Test (windows-latest) — two Windows verbatim-path tests (tools::shell::tests::readonly_operands_are_workspace_bounded_and_symlink_aware, tools::subagent::tests::read_only_inspection_roles_execute_pwd_and_absolute_git_log).

Both are fixed by #5610, which is waiting to land. Anything else that goes red is worth your attention.

Sorry this sat for so long without a real signal. Same treatment applied to #5592 and #5594.

[Hmbown]

Merged onto the v0.9.12 integration branch in 397b9cb; re-verified in-tree: /relaunch wiring in tui/event_loop.rs, tui/app.rs, and the control-socket relaunch verb in tui/control_socket.rs, with the portable argv-construction test suite. Closing as landed — thanks @M-Maciej!