Add git-tree: local Git commit graph viewer

[Microbiosis]

Summary

Adds git-tree — a MiniApp that inspects a local Git repository's commit history.

Plugin directory: plugins/microbiosis/git-tree/
Plugin ID (name in .minimax-plugin/plugin.json): git-tree
Author (plugin.json): redmingwei

This is a re-submission of the previously closed PR #7. The five bugs below
were found by running the plugin for real — live server plus a real browser
driven by Puppeteer — and are fixed in this branch. All five were invisible to
syntax/import smoke tests; each one was reproduced first, then fixed, then
re-verified through the same interfaces.

Bugs fixed since #7

1. Paginated graph layout was per-page, not per-window. buildGraph() is
   stateful across rows (lane colour reuse, merge-path detection,
   lockedFirst), so laying out page N in isolation disagreed with the pages
   around it: a branch opened on page 1 lost its lane on page 2, and merges
   stopped resolving once scrolled past the first page. Now the whole
   accumulated window is laid out. git log -n offset+limit+1 already fetched
   those rows, so this costs no extra git call; only the current page's commits
   go over the wire.
2. Client concatenated the graph geometry arrays. They are absolute-indexed
   and describe the whole accumulated list, so concat duplicated every page's
   rows and left the canvas sized to the first page only. They now replace,
   followed by applyGraphSize() + renderCanvas() so rows past page 1 get
   lanes and dots.
3. A cleared filter could not be persisted. sanitizePrefs() dropped empty
   strings, so an empty ref — how the client says the filter was cleared —
   was silently discarded and the merge resurrected the old value on reload.
4. An oversized prefs body reset the connection instead of answering.
   req.destroy() tore the socket down before sendJson could write the
   response, so the client saw a bare connection reset rather than the designed
   error body. Now the stream drains and the caller returns a real
   413 body_too_large.
5. Two normalisation bugs. A repos.json written by a Windows editor
   carries a UTF-8 BOM that JSON.parse rejects, which made an explicitly
   configured allowlist fail silently and fall back to discovery. And
   buildRegistry() pushed raw D:/foo paths while defaultRepo handed the
   client resolve()d ones, so the repo dropdown could not match its own
   option list and rendered as "nothing selected".

Features

• Swim-lane commit graph rendered as a single SVG canvas (lanes, paths, dots, hover highlight, selection ring); the lane-assignment algorithm in miniapp/node/git-graph.mjs is a JavaScript port of zai-org/ZCode's layoutAlgorithm.ts / layout.ts, which are Apache-2.0. Attribution is preserved in LICENSE and README.md.
• Stats panel: total commits, branches, tags, working-tree changes (7 parallel git commands, cached 30 s per repo).
• Graph pane: git log <ref> --topo-order + optional --grep / --author; up to 400 rows per call; result server-validated, client renders one SVG.
• Commit detail: subject, refs, file changes table, body. Two independent views — inline (collapsible below the list) and a right-pane (always on).
• Filter preferences (theme, repo, ref, q, author, interval) persisted to <dataDir>/prefs.json; merged writes via /api/prefs (POST never wipes siblings), 400 ms client-side debounce.
• Optional auto-refresh (5 / 10 / 30 / 60 s) with manual refresh still available; preserves selected commit, scroll position, and inline-detail state across ticks; countdown chip next to the refresh button.
• Per-command git timeouts: 10 s quick / 15 s medium / 30 s heavy; client api() caps at 35 s with AbortController. API responses ≥ 256 bytes are gzipped when Accept-Encoding: gzip is sent.
• Portability fallback for repos.json empty installs: when the user has not authored repos.json and the plugin is not installed inside any git tree, the registry also scans ~/Code, ~/Projects, ~/repos, ~/workspace, ~/src, ~/source, ~/dev, ~/work, ~/Documents, ~/git (case-insensitive on Windows/macOS), plus on Windows every mounted drive root (A:\ … Z:\). Windows system hives (Program Files, Windows, Users, ProgramData, $Recycle.Bin, …) and macOS resource dirs (Library, Applications, System) are filtered so widening to drive roots cannot recurse into %ProgramFiles%. The fallback only activates when no other discovery source is present, so users with an explicit repos.json are unaffected.

File layout

plugins/microbiosis/git-tree/
├── .minimax-plugin/plugin.json     # manifest (name, displayName, version, license)
├── docs/preview.jpg                # preview image (synthetic data)
├── icon.png
├── miniapp/
│   ├── client/index.html          # single file, single SVG canvas, inline script
│   ├── miniapp.json
│   └── node/
│       ├── git-graph.mjs         # lane-assignment algorithm (port from ZCode)
│       ├── repos.json            # ships empty by design
│       └── server.mjs            # entry; binds the host listen port
├── package.json
├── LICENSE                        # Apache-2.0 with ZCode attribution block
├── README.md                      # English
└── README.zh-CN.md                # 简体中文

What was tested

• MiniMax Code desktop 3.0.73.166, Windows 10.0.26200 (x64).
• Synthetic git repository with 5 commits, 1 merge, 2 branches — preview screenshot in docs/preview.jpg is generated from this synthetic data.
• End-to-end check of the portability fallback on this Windows host confirmed discovery of git repositories under D:\ and E:\ without any repos.json configuration.
• Full end-to-end run after the five fixes, against a real server bound to the host listen port and driven by a real Chrome via Puppeteer:
  • API harness: 47/47 passing — repo discovery, overview, graph pagination (including the multi-page lane-continuity cases that motivated fix 1), commit detail, and prefs read/write (including the empty-string and oversize-body cases behind fixes 3 and 4).
  • Browser harness: 24/24 passing — real DOM/canvas interaction, pagination, filters, detail panes, refresh, persistence across reload.
  • Additionally verified through the installed Host copy (not just the source tree): the process is really listening, GET /git-tree returns 200, and the fixed endpoints return the corrected payloads.

Not verified: macOS and Linux. The portability fallback is implemented for both platforms (Unix home parent + common dev directories; Windows drive roots), but only the Windows path has live confirmation.

Submission checklist

• Plugin directory placed under plugins/<github-username>/<plugin-id>/.
• Plugin ID is unique in the repository (no git-tree collision).
• .minimax-plugin/, package.json, miniapp/, and runtime assets preserved.
• English README.md (with mutual link to README.zh-CN.md); documented install path, verified client version + OS, configuration, and required file / network access.
• LICENSE (Apache-2.0) with explicit attribution to zai-org/ZCode for the ported layout algorithm.
• No node_modules/, no secrets, no real session data. Screenshot uses synthetic data.
• Plugin can be copied and used independently; no dependency on other directories in this repository.
• New row added to both root READMEs (English and 简体中文) and a preview block.

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