Wire TUI test harness as tier in /auto Test Manifest

[jsavin]

Rationale

PR #788 added tools/tui-tests/ — a tmux-driven test harness for the boxen --debug-tui REPL. It is intended as a skippable tier in the project's /auto Test Manifest (run if tmux is available; otherwise skipped with a note).

Wiring was deferred from PR #788 because CLAUDE.md was in an unrelated unmerged state (AGENTS.md UU + CLAUDE.md modified+staged) at session start, and editing it would worsen the pending state.

Desired Outcome

Once the AGENTS.md merge is resolved, update both ## /auto Test Manifest sections in CLAUDE.md (there are two; lines 127 and 227 as of 4ce8a09cd) to add a TUI tier:

- **TUI**: `./tools/tui-tests/run.sh` (skippable — requires `tmux`; HTML
  snapshots additionally require `aha` (brew install aha))

Update the table semantics text if needed to clarify that skippable
means "run if infra is available; otherwise note skip in PR description"
(which it already does).

Exit Criteria

• Both ## /auto Test Manifest sections in CLAUDE.md mention the TUI tier
• /auto runs tools/tui-tests/run.sh when tmux is in PATH
• /auto notes "TUI tests skipped — tmux not installed" in PR description otherwise
• CLAUDE.md still passes the existing pre-commit hook validator

Context

• Source: PR feat(tests): TUI test harness for boxen --debug-tui REPL #788 deferred work
• Block: requires resolving the pre-session AGENTS.md merge state
• Refs: Interactive REPL debugging: provide a debug transport for bare linenoise sessions #691