feat: refine console and control center UI

[chen-985211]

💡 Change Scope

• Small Change: Fast feedback, localized UI/logic, low-risk.
• Large Change: New feature, cross-boundary logic, runtime-risk (persistence, IPC, lifecycle, recovery).

📝 What Does This PR Do?

Refines the OpenCove console into a calmer, denser productivity-tool UI while preserving existing behavior and state ownership.

• Adds semantic surface, text, interaction, focus, toggle, theme-preview, elevation, and overlay-layer tokens.
• Introduces reusable Button, IconButton, Toggle, SettingRow, Dialog, Popover, and dismissable-layer primitives with unit coverage.
• Reworks Control Center to the approved 360 px compact layout, removes its sidebar control, calibrates typography and switch colors, and keeps all five themes accessible.
• Refines settings, header, sidebar, command/search surfaces, messages, notifications, workspace canvas, minimap, node chrome, remote UI, and worktree surfaces across dark, light, Ember, and Ember Light themes.
• Adds a staged UI style guard to prevent raw component colors, undeclared tokens, and theme-branch drift.
• Defines semantic nested-dialog and dialog-popover layers, fixing pointer interception for remote directory browsing and prompt-template menus.
• Integrates the merged Settings hierarchy from Refine Settings hierarchy and visual design #299 with the shared Dialog focus lifecycle, semantic UI tokens, and scoped legacy toggle styles without reintroducing the Control Center sidebar action.

No executable architecture-rule impact.

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🏗️ Large Change Spec (Required if "Large Change" is checked)

1. Context & Business Logic

The console had inconsistent visual hierarchy, duplicated theme branches, raw component colors, and competing overlay conventions. This PR consolidates the renderer UI around restrained tool-style semantic tokens and reusable accessible primitives. User-visible behavior remains the same except that Control Center no longer exposes the sidebar toggle, as requested; sidebar pinning and shortcuts remain available through their existing owners.

2. State Ownership & Invariants

• AgentSettings remains the authoritative owner of theme, minimap, standby-banner, UI font-size, and sidebar intent. The new components only project and dispatch changes; they do not introduce mirrored persistent state.
• Exactly one Control Center theme radio is selected, and all toggles preserve native switch semantics and keyboard focus behavior.
• Overlay order is deterministic: normal menus/popovers remain below dialogs; nested dialogs and dialog popovers remain above their parent dialog; notifications remain topmost.
• Closing Dialog/Popover surfaces restores focus without leaking listeners or allowing a lower layer to intercept pointer input.

3. Verification Plan & Regression Layer

• Unit: UI primitives, anchored placement, focus trapping, dismissable layers, toggle semantics, and style-guard rules.
• E2E: Control Center dark/light/Ember screenshots, 360 px proportions, switch colors, typography ratios, sidebar-control removal, theme selection, narrow viewport, large UI text, settings focus semantics, remote directory browsing, and prompt-template nested overlays.
• Full gate: pnpm pre-commit passed with 91 unit-test files / 288 tests and 257 Electron E2E tests passed; 47 platform/manual cases skipped as expected.

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✅ Delivery & Compliance Checklist

• My code passes the ultimate gatekeeper: pnpm pre-commit is completely green.
• I have signed the CLA if required (the automated check may request confirmation).
• I have included new tests to lock down the behavior.
• I have strictly adhered to the DEVELOPMENT.md architectural boundaries.
• I have attached a screenshot or screen recording (Playwright dark/light/Ember/narrow captures were generated and reviewed locally; upload via the GitHub UI is still required so review-only media is not committed).
• I have updated the documentation accordingly (no external feature or architecture contract changed; the style guard is integrated into the repository gate).

📸 Screenshots / Visual Evidence

Playwright generated and validated the following review captures locally:

• Control Center: dark, light, Ember, and narrow viewport with large UI text.
• Settings: dark/light themes, narrow layout, every primary page, Worker hierarchy, search keyboard behavior, modal focus containment, and focus restoration.
• Remote UI audit surfaces.

Per repository policy, these review-only images are not committed. They can be uploaded directly to this PR through the GitHub UI.