feat: add GitHub actions to comment, merge, close, and reopen

[osolmaz]

Summary

ghzinga could only watch a PR or issue; acting on it still meant switching to the browser.
This change adds GitHub write actions to the TUI: comment, merge, close, and reopen, right from the viewer.
Every step works with the mouse alone or the keyboard alone, comments are written in an in-app multiline composer, and the view refreshes from GitHub after each action so it never shows guessed state.
Actions only appear when the viewer is authenticated and actually allowed to act, and the server stays the final authority.

What Changed

The feature follows the existing Elm-style architecture: pure domain types and reducer logic, a GraphQL adapter for the writes, and a background pipeline that mirrors how fetches already work.

• Domain (src/domain/action.rs): ResourceAction, MergeMethod, ActionKind, and pure available_actions gating based on a new ActionContext (GraphQL node id, viewerCanUpdate, locked) plus repository-allowed merge methods, all fetched with the existing resource query.
• GitHub adapter (src/github/mutations.rs): GraphQL mutations for addComment, closeIssue/reopenIssue, closePullRequest/reopenPullRequest, and mergePullRequest, reusing the existing authenticated transport. The unauthenticated REST fallback stays read-only.
• UI: an [actions] footer button and A key open a context-sensitive menu; close/reopen and merge get confirm modals (merge with a method picker limited to what the repo allows); comments get a multiline composer modal with clickable submit/cancel buttons, click-to-place cursor, wheel scroll, and width-aware wrapping shared between rendering and input mapping (src/app/composer.rs).
• Pipeline (src/fetch.rs, src/runner.rs): submissions spawn in the background, results come back over a dedicated channel, state is finalized on the main thread, and a successful action triggers an automatic refresh. Failures surface the API error in the status line and keep an unsent comment draft.
• Terminal: bracketed paste is now enabled, so multi-line paste arrives as one event instead of a stream of fake keypresses.
• Mouse/keyboard parity is structural: every operation is one reducer arm reachable from both a HitTarget and a key binding.

Testing

All local gates pass, and the new flows are covered by reducer, render, adapter, and pipeline tests.

• cargo fmt --check, cargo check --all-targets, cargo clippy --all-targets --all-features -- -D warnings
• cargo test: 597 tests pass (573 lib + architecture + CLI), including ~50 new tests for action availability, menu/confirm/composer key and click flows, paste handling, mutation guards, and modal rendering with hit-area assertions
• cargo llvm-cov --fail-under-lines 85: passes at 85.86% lines
• cargo audit, slophammer-rs check . and dry . (0.4.0): clean
• Terminal captures regenerated with the new binary and all capture/mouse-smoke validators pass; manifests re-stamped
• cargo mutants --in-diff (executing run) was started locally; the CI gate runs the same check on this PR
• Not tested locally: real mutations against GitHub (comment/merge/close on a live repo) — exercised after merge

Risks

The riskiest part is state drift after a write, and the design avoids it by never patching state locally: after any successful action the resource is refetched from GitHub.

• Server-side rejections (branch protection, merge conflicts, permissions) surface as status-line errors; the UI only pre-filters using viewerCanUpdate, locked, and allowed merge methods, so a rare 403/409 is still handled gracefully.
• The composer is a new hand-rolled editor; its wrapping/cursor logic is pure and unit-tested (multibyte, wide chars, CRLF paste, wrap boundaries), and v1 deliberately omits selection/undo.
• Offline fixture mode and the unauthenticated fallback hide all actions, so existing capture-based rendering is unchanged except for the new help line.

[osolmaz]

Final report

Merged as 9319b58. GitHub write actions (comment, merge, close, reopen) are now available in the TUI behind the [actions] footer button and the A key, fully usable by mouse alone or keyboard alone.

Review

Six Codex review rounds (gpt-5.6-terra, high reasoning) against main. All P1s and all but one P2 were fixed:

• post-action refresh routed to the originating tab, skipped when the tab closed or navigated away, with no stuck pending state
• confirmation/menu/submit shortcuts require unmodified keys (Ctrl-Y, Ctrl+Alt+S, etc. can no longer act)
• comment drafts are tab-scoped; the posting draft is frozen and only the composer holding the posted body is closed
• deferred post-action refreshes survive an in-flight fetch instead of being wiped by its completion
• completion messages never leak onto a resource the tab navigated to
• zero-width Unicode counts as zero columns in composer wrapping/cursor/click math

Skipped (with rationale): tracking the posting composer by identity instead of body — only observable when a replacement draft is byte-identical to the comment that just posted, in which case nothing is lost.

Validation

• cargo fmt --check, cargo check --all-targets, cargo clippy --all-targets --all-features -- -D warnings: clean
• cargo test: 660 tests pass (636 lib + 15 architecture + 9 CLI)
• cargo llvm-cov --fail-under-lines 85: 86.51% lines
• cargo audit, slophammer-rs check ., slophammer-rs dry . (0.4.0): clean
• cargo mutants --in-diff (executing): first full run 108 missed / 405 → all addressed via ~90 new tests, three structural rewrites that removed unkillable-equivalent mutants, and three justified boundary exclusions in .cargo/mutants.toml; a verification run had 0 missed at the point it was cut short on request, and the PR's CI run exercises the full gate
• Terminal captures regenerated against the new binary; all capture and mouse-smoke validators pass; manifests re-stamped
• Not tested locally: live mutations against real GitHub resources (needs a disposable issue/PR)

Mutation testing also surfaced one real bug beyond review findings: deferred refresh entries could be dropped when a fetch raced in; the queue now retains them.

[osolmaz]

Testing comments inside ghzinga