feat: add read-only project file explorer and preview

[nonlooped]

Summary

• Adds a Files tab to the context pane: a lazy-expanding project tree (reusing the existing gitignore-aware file list), with git-state badges and Recent/Frequent quick-access sections.
• Selecting a file swaps in a read-only preview: breadcrumbs, size/modified metadata, git-state badge, syntax-highlighted code and rendered Markdown (via the existing Streamdown/@streamdown/code pipeline), and image previews.
• "Open in editor" and "Reveal in Explorer" reuse the existing editor-launch IPC; right-click still offers the existing file context menu.
• Recent/frequent file access is tracked per project in NativePi's own persisted state (not Pi's), alongside the existing pinned-project/chat data.

Scope notes

• Read-only by design: no editing, no new agent tools, nothing that reaches Pi's agent loop or model output — this only reads local files and existing Git/editor IPC NativePi already had.
• No new directory-listing IPC was needed: the file tree is built client-side from the existing listProjectFiles (git ls-files-based, already gitignore-aware).

Test plan

• bun run typecheck
• bun run build
• bun test (152 pass)
• Manual run in the dev app — not done, per AGENTS.md's rule against starting a long-lived dev server; would need manual verification by a maintainer (open a project, switch to the Files tab, expand folders, preview a text/markdown/image file, use Open in editor / Reveal in Explorer).

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
nativepi	Ignored	Preview	Jul 31, 2026 10:20am

[chatgpt-codex-connector]

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