feat: add a setting to disable git commit attribution

[frarredondo]

Summary

• Adds a global gitAttributionEnabled setting (default true) that gates the GIT_COMMITTER_NAME/GIT_COMMITTER_EMAIL injection Pane adds to every commit made through its terminals, CLI panels, and internal git operations
• The existing "Include Pane footer in commits" setting only controls the Co-Authored-By trailer — it never touched the committer identity, so commits always showed as "committed by runpane" on GitHub with no way to opt out
• New getGitAttributionEnv() helper in attribution.ts centralizes the default-true gating logic, wired into all 9 injection sites (terminal panels, terminal sessions, run commands, CLI panels, project init, worktree operations ×3, editor commits ×2)
• New "Attribute commits to Pane" toggle added to Settings → Worktrees & Git, right below the existing footer toggle

Fixes #343

Test plan

• pnpm typecheck clean across all workspaces
• pnpm lint — 0 errors (pre-existing warnings only, none in touched files)
• pnpm --filter main test — new attribution.test.ts unit tests pass; updated terminalPanelManager.test.ts mock; full suite green aside from 3 pre-existing native-module ABI failures unrelated to this change
• Manual verification in an isolated dev instance (separate PANE_DIR, throwaway git repo): toggled setting off → new terminal panel commit shows the user's own git identity as committer; toggled back on → new terminal panel commit shows Pane <runpane@users.noreply.github.com> again
• Confirmed the one documented limitation: toggling only affects newly-spawned terminals/panels — an already-running panel keeps its launch-time env until reopened

[parsakhaz]

Approved based on a read-only implementation review against issue #343.

Evidence checked:

• The new gitAttributionEnabled flag is default-on and gates the Pane GIT_COMMITTER_NAME / GIT_COMMITTER_EMAIL injection through getGitAttributionEnv().
• All attribution injection paths from the issue are covered: terminal panels, legacy terminal sessions, run commands, Claude/Codex CLI panels, project initialization, worktree internal commits, and editor commit/retry paths.
• Config typing and persistence are wired on both main/frontend sides, and the setting is reachable in Settings > Worktrees & Git.
• Node 22 checks passed locally on the PR head:
  • pnpm typecheck: PASS
  • pnpm lint: PASS, 0 errors; existing warnings only
  • Focused tests: pnpm --filter main exec vitest run src/utils/attribution.test.ts src/services/terminalPanelManager.test.ts: PASS, 16 tests

Non-blocking nuance: terminal-panel WSL startup still lists GIT_COMMITTER_NAME and GIT_COMMITTER_EMAIL in WSLENV even when attribution is disabled. Since the gated env no longer sets those variables, this should be harmless in normal use, but it would be reasonable future hardening to omit those names from WSLENV when attribution is disabled.

Recommendation: approve and merge.