feat(review): Aone Code read path (second review-platform provider)

docs/design/2026-08-15-review-aone-provider.md

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+# Phase 2: Aone Code read path for /review
+
+> Status: draft. Parent: `docs/design/2026-08-13-review-platform-provider-abstraction.md`.
+> Phase 0+1 (GitHub provider) merged as #9096 (`dc7e234876`).
+
+## Problem
+
+Phase 0+1 added the `ReviewPlatformReader` seam with one provider (GitHub).
+`/review` still cannot review a MaxCompute CR on Aone Code (`odps_src`), which
+is the motivating target. This phase adds the Aone read path so a local review
+of an Aone CR works end to end (diff + worktree + issue evidence + agent
+findings), and `--comment` on an Aone target refuses cleanly.
+
+## Verified platform facts (re-confirmed 2026-08-15 against `maxcompute/odps_src`)
+
+| Capability     | a1 CLI / git                                                                                                                                  | Notes                                                                                                                                                                                                      |
+| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| MR metadata    | `a1 repo mr view <global-id> --repo <g/p> -f json` → `mergeRequest{sourceBranch, targetBranch, title, description, detailUrl, author, state}` | `sourceBranch` is the head SHA (AGit-Flow); `targetBranch` is base; `detailUrl` = `https://code.alibaba-inc.com/<g>/<p>/codereview/<global-id>`; **no** additions/deletions/changedFiles (compute locally) |
+| Fetch ref      | `git fetch <remote> refs/merge-requests/<global-id>/head:<ref>`                                                                               | head SHA matches `sourceBranch`; merge-base vs `targetBranch` and `git diff` both computable (probe: MR 29295886 → 51 files, 2930+/114-)                                                                   |
+| id/iid         | `mr view`/`mr list` carry both `id` (global) and `iid`                                                                                        | refs/`mr view` key on the **global id**; Aone CR URL is `/codereview/<global-id>`                                                                                                                          |
+| Discussion     | `a1 repo mr comment list --mr <id> --repo <g/p> -f json` → array with `id, note, path, line, author, closed, outdated, isAiComment`           | **text is in `note`** (not `body`); `body` is empty                                                                                                                                                        |
+| Issue evidence | `a1 repo mr workitem list --mr <id>` → `[{id, subject, link, assigned_to}]`; `a1 project workitem get <id>` for body/comments                 | workitem id = the `#AONE_ID` in the commit title                                                                                                                                                           |
+| Diff listing   | `a1 repo mr diff <id>` (file list) / `<id> <file>` (per-file)                                                                                 | only needed in lightweight mode; the primary path diffs via git after fetching the ref                                                                                                                     |
+| CI status      | `a1 repo mr status <id>`                                                                                                                      | presubmit-equivalent (read-only)                                                                                                                                                                           |
+
+## Proposed scope (vertical slice — confirm before implementing)
+
+**In scope (makes local Aone review work):**
+
+1. `lib/platform/aone-client.ts` — a1 transport sibling to `lib/gh.ts`,
+   replicating its contract: `execFileSync` without shell, transient retry only
+   on idempotent reads, byte mode for diffs, actionable auth check
+   (`a1 auth whoami`), and `--repo` threading (Aone has no `GH_HOST` analogue;
+   the repo coordinate is passed per call).
+2. `lib/platform/aone.ts` — implements `ReviewPlatformReader`:
+   `resolveRepo` (parse the clone's origin URL → `gitlab.alibaba-inc.com/<g>/<p>`),
+   `getPrMeta` (mr view → sourceBranch/detailUrl), `getClosingIssues` (workitem
+   list), `getIssue` (workitem get), `fetchDiff` (git-based after fetching the
+   ref; a1 per-file diff only for lightweight mode), `getCommentBody` (read
+   `note` from comment list).
+3. **Detection** in `registry.ts`: select the platform from (a) an explicit
+   `--host` whose host is an Aone host, (b) an explicit `--remote` URL on an
+   Aone host, else (c) the cwd clone's origin. An explicit NON-Aone
+   host/remote beats the cwd probe (so an explicitly-GitHub subcommand run
+   from an Aone clone is not hijacked). The four reader-backed subcommands
+   (meta/issue-context/fetch-diff/comment-body) thread `--host` into
+   detection; fetch-pr threads the remote URL. (An explicit `--platform`
+   override is deferred — an explicit `--host` already serves as the
+   practical override.)
+4. `fetch-pr.ts` — provider-aware refspec + metadata: Aone uses
+   `refs/merge-requests/<global-id>/head` and mr-view metadata (no
+   additions/deletions — compute from the fetched diff). This is the enabler
+   for worktree mode, build/test, and the full agent review.
+
+**Deferred to a follow-up (degrade gracefully in this phase):**
+
+- `pr-context.ts` discussion rendering (inline threads, review summaries,
+  ledger): Aone has comments but no GitHub review-summary model. For v1, Aone
+  runs enter the existing **context-unavailable** mode (verdict caps at
+  COMMENT; findings still generated). Note Agent 0 (issue fidelity) is gated
+  on `pr-context` success, so it is SKIPPED on Aone too — `issue-context`
+  works standalone for the workitem evidence but is not wired to Agent 0.
+- `comment-status.ts` anchor-status and `presubmit.ts` CI checks: skip for
+  Aone v1 (the skill already handles their absence).
+
+`--comment` on an Aone target refuses with a clear message (posting is Phase 3).
+
+## Key design decisions
+
+- **Transport is a sibling, not a refactor of gh.ts.** `isOwnerRepo`,
+  `HOSTNAME_RE`, and the host-routing state (`setGhHost`/`resolveGhHost`/
+  `getGhHost`) are currently gh.ts-owned. Aone has no global host routing
+  (repo coordinate per call), so the shared surface is the _validators_
+  (move `isOwnerRepo`/`HOSTNAME_RE` into `lib/platform/` or a shared
+  `lib/validate.ts`) — not the gh host state.
+- **Detection is cheap and explicit.** Remote-URL host is already parsed by
+  `match-remote`'s matcher; the reader threads `--host`/the remote URL into
+  detection. An explicit non-Aone signal beats the cwd probe.
+- **Diff is git-based.** Fetching the MR ref makes Aone diffs identical to
+  GitHub's (merge-base + unified diff), so `plan-diff`/chunking need no
+  Aone branch. `a1 mr diff` is only the lightweight fallback.
+- **Global id is the review number.** Aone CR URLs carry the global id; the
+  reader uses it for refs/`mr view`/comments/workitems.
+
+## Files affected
+
+- New: `lib/platform/aone-client.ts`, `lib/platform/aone.ts` (+ tests).
+- Modified: `lib/platform/types.ts` (add `'aone'` to `PlatformKind`),
+  `lib/platform/registry.ts` (detection), `fetch-pr.ts` (provider routing),
+  possibly a shared validators module, `parse-args.ts` (Aone CR URL grammar
+  `/codereview/<id>`), `meta.ts`/`issue-context.ts`/`fetch-diff.ts`/
+  `comment-body.ts` (platform selection + non-GitHub `--host` semantics),
+  `SKILL.md` (Aone target handling + lightweight/detect guidance),
+  `docs/users/features/code-review.md`.
+
+## Open questions
+
+1. **Scope**: ship the minimal slice (reader + detection + fetch-pr;
+   pr-context/comment-status/presubmit degrade), or also make `pr-context`
+   render Aone comments (bigger lift)? Recommendation: minimal slice.
+2. Aone comment threading (`closed`, `outdated`) vs GitHub's
+   `in_reply_to_id`/`line` model — only matters if `comment-status` joins.
+3. build/test (Agent 7) on a Bazel monorepo needs a repo-config escape hatch
+   (already flagged out of scope in the parent doc); confirm it degrades
+   cleanly rather than attempting a full `bazel build`.