feat: replace approval modals with a responsive dock

[ken-jo]

Summary

• replace every foreground approval modal (tool, agent action, rationale, MCP elicitation, and out-of-directory) with one bounded, nonmodal approval dock
• preserve fail-closed approval, FIFO, sealed rationale identity, durable decision extras, keyboard behavior, focus restoration, and narrow-window containment
• remove legacy page-level back/close controls so the shared navbar owns history; preserve Settings' narrow list -> detail -> internal back flow and flush debounced saves on navigation
• show monthly API provider/model and separate subscription runtime/model usage in Insights using the existing usage range source
• add CDP/E2E coverage for navbar history, 460px Settings two-depth, nonmodal approval containment, and Insights usage breakdowns
• keep local transient worktrees out of duplicate-helper scans and lock in resolved knip/test-typecheck baseline debt

Root cause

The August 8 approval migration only moved out-of-directory requests away from Radix Dialog; tool, agent-action, rationale, and MCP approval requests still used the old modal. The apparent Settings mobile regression was caused by a CDP/E2E window resize that was not restored—the panel-width two-depth implementation itself remained intact.

Validation

• full pre-push hook passed
• typecheck, test-typecheck self-test/baseline, knip baseline, duplicate-helper policy
• 1,012 test files passed (1 skipped); 12,885 tests passed (43 skipped)
• full production build and source/i18n/import-cycle/generated-asset policies passed
• focused Electron UI E2E: approval dock, navbar/Insights, narrow Settings, release approval card
• live CDP at 463x842: legacy/modal selectors 0, navbar visible, narrow Settings list/detail/back restored, Insights provider/model rows visible, horizontal overflow 0
• independent integration, accessibility/security, and residual-selector reviews found no release blockers