feat: redesign projects controls and settings navigation

[klioen]

Summary

Move the Projects-panel toggle into the Projects header, move Settings to the Projects footer, and replace the Settings modal with an Orca-inspired full-window navigation surface. This follow-up also fixes the Windows path normalization regressions reported by the merged PR #60 CI run.

Related work

• Follow-up to feat: add secure file and source control workflows #60
• Accepted change artifact: docs/orca-aligned-settings/change.md

Changes

• Put the Projects toggle beside the SpireCode identity and keep a compact top-left reopen action when the panel is collapsed.
• Put the Settings action at the bottom of the Projects panel and remove Settings, Projects, and theme controls from the workspace top-right cluster; theme selection now exists only in General Settings.
• Replace SettingsDialog with a full-window SettingsPage that has a stable title strip, explicit Back to workspace action, autofocus search, grouped navigation, active-page semantics, and a centered scrollable content column.
• Restyle setting rows and resource groups as neutral contained surfaces while preserving all existing settings APIs and persistence behavior.
• Keep readiness failures opening Agent settings automatically; manual entry now opens General.
• Normalize filesystem mutation relative paths, discovered Git roots, and displayed settings resource paths across Windows and POSIX. This addresses the four Windows failures from feat: add secure file and source control workflows #60.
• Add bilingual copy, interaction/style tests, changelog text, and a standard SDLC change artifact.

Risk and boundaries

• Regression risk: Medium. The Workbench navigation shell, Projects rail, and Settings layout change, but no IPC contract, persistence schema, or Main/Renderer authority boundary changes.
• Security/privacy impact: None. Existing typed settings APIs and filesystem/Git validation remain unchanged.
• Data or configuration migration: None.
• Platform/package impact: Renderer layout changes on all desktop targets. Windows path normalization fixes affect Main output formatting and canonical project identity.
• Rollback approach: Revert this PR; no stored state requires migration.

Verification

pnpm check
# 68 test files, 453 tests passed; release tests passed

pnpm build
# Renderer and Electron Main builds passed

pnpm vitest run electron/domains/filesystem/filesystem.test.ts electron/domains/projects/projects.test.ts electron/domains/settings/settings.test.ts
# 3 files, 38 tests passed

git diff --check HEAD
# passed

pnpm bundle
# macOS arm64 App signature, packaged-app smoke, and DMG smoke passed

• Tests cover new or changed behavior.
• pnpm check passes locally.
• macOS arm64, Windows x64, and Linux x64 target-host CI bundle/smoke jobs passed.
• No screenshot is attached; component interaction and CSS contract tests cover the new layout.

Contributor checklist

• I read CONTRIBUTING.md and the repository AGENTS.md.
• The change follows docs/orca-aligned-settings/change.md.
• Renderer/Main authority, relative-path validation, Git argument arrays, and credential boundaries remain intact.
• Public docs and CHANGELOG.md are updated.
• The diff contains no credentials, private data, dependency updates, or generated release artifacts.
• I reviewed the diff for correctness, security/privacy, and compliance with accepted scope.