fix(cli): declare the transcript viewer's mid-turn disposition

[Astro-Han]

Summary

main does not typecheck. MakaSlashCommand.midTurn became required so every handler has to state whether it is safe to run while a turn is in flight; /transcript (#2999) landed in parallel and never got an answer:

packages/cli/src/pi-tui-runner.ts(2877,5): error TS2741: Property 'midTurn' is missing in type
'{ description: string; run: (parts: string[]) => void; }' but required in type
'Omit<MakaSlashCommand, "aliases" | "name">'.

Neither PR was wrong on its own — the conflict is semantic, so both merged green and main broke. The viewer is a full-screen overlay over the same TUI the running turn paints into, which is the picker case 'refuse' exists for, so that is its declared answer.

Refs #2999

Verification

• npm run build — passes with this change, fails on main without it
• npm run format:check — clean
• npm test --workspace maka-agent — 371 pass, 0 fail

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Claude Code diagnosed the cross-PR type break and wrote the one-line declaration and its comment. The human contributor reviewed the diff and the disposition choice.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

The compiler is the test: main fails to build without this change.

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

/transcript is now refused mid-turn instead of opening over a running turn.

[Astro-Han]

Superseded by #3459, which landed the same declaration on main in b434a49. main builds again, so this is redundant — closing.

One correction worth recording for anyone who hits this next: the value that landed is midTurn: 'local', not 'refuse'. The type's own doc comment draws the line at whether the handler enters runControl — 'local' requires the handler to be independent of the running turn, 'refuse' is for anything that mutates session state or opens a picker the turn would race. showTranscriptViewer only calls tui.showOverlay and never touches runControl, so 'refuse' would have compiled while silently disabling /transcript exactly when reading back is most useful.

Review assisted by AI (Claude Opus 5).