fix(review-round-3b): propagate worktreeListDetailed failures via Result

CodeRabbit identified that worktreeListDetailed silently returned []
on `git worktree list` failure, making the try/catch in
checkBranchCollisions dead code. The pre-check would then pass as
"collision-free" despite never having queried git — violating FR-009
case (b), which requires marking the repo status="failed" and
excluding it from subsequent mutation.

Changes:
- git.ts: worktreeListDetailed now returns Result<WorktreeEntry[],
  string>. Empty array on parse success, Result.err(gitError) on git
  failure.
- workspace-create.ts checkBranchCollisions: replace try/catch with
  `if (!result.ok)` branch; cache map now stores WorktreeEntry[]
  directly.
- workspace-create.ts isWorktreeHealthy: treat git failure as
  unhealthy so reconcile re-runs `git worktree add` (which will
  surface the underlying git error through normal error paths).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: wentaoyuan

src/plugin/worktree/git.ts

@@ -225,9 +225,9 @@ interface WorktreeEntry {
  * @param repoRoot - Absolute path to the repository root
  * @returns Array of WorktreeEntry (includes the main worktree)
  */
-async function worktreeListDetailed(repoRoot: string): Promise<WorktreeEntry[]> {
+async function worktreeListDetailed(repoRoot: string): Promise<Result<WorktreeEntry[], string>> {
 	const result = await git(["worktree", "list", "--porcelain"], repoRoot)
-	if (!result.ok) return []
+	if (!result.ok) return Result.err(result.error)
 
 	const entries: WorktreeEntry[] = []
 	let currentPath: string | null = null
@@ -253,7 +253,7 @@ async function worktreeListDetailed(repoRoot: string): Promise<WorktreeEntry[]>
 		entries.push({ path: currentPath, branch: currentBranch })
 	}
 
-	return entries
+	return Result.ok(entries)
 }
 
 // =============================================================================

src/plugin/worktree/workspace-create.ts

@@ -24,6 +24,7 @@ import { loadWorktreeConfig } from "./config"
 import {
 	type Result,
 	Result as R,
+	type WorktreeEntry,
 	branchExists,
 	createWorktree,
 	git,
@@ -210,9 +211,9 @@ async function resolveBaseBranch(repoPath: string): Promise<Result<string, strin
  *       FR-009 mandates per-repo `status="failed"` and exclusion from
  *       subsequent steps for that repo only; other repos continue.
  *
- * The function never throws on a per-repo `worktreeListDetailed` failure —
- * the failure is captured into `preCheckFailures` and the rest of the
- * pre-check continues so all repos get evaluated.
+ * `worktreeListDetailed` surfaces git errors via its `Result` return (not
+ * throws), so those failures are captured into `preCheckFailures` and the
+ * rest of the pre-check continues so all repos get evaluated.
  *
  * @param plans         Planned repo worktree actions (only "create" and
  *                      "retry" plans require pre-check; "reuse" already
@@ -240,7 +241,7 @@ export async function checkBranchCollisions(
 	// Collect all worktree entries per unique repo root (dedup in case
 	// multiple plans reference the same repo root — shouldn't happen but
 	// defensive).
-	const worktreeCache = new Map<string, Awaited<ReturnType<typeof worktreeListDetailed>>>()
+	const worktreeCache = new Map<string, WorktreeEntry[]>()
 	// Repo roots whose pre-check has already failed; skip subsequent plans
 	// referencing the same repo to avoid duplicate failure entries.
 	const failedRepoRoots = new Set<string>()
@@ -254,21 +255,22 @@ export async function checkBranchCollisions(
 		if (failedRepoRoots.has(repoRoot)) continue
 
 		// Fetch detailed worktree list (cached per repo root). On failure,
-		// record it as a per-repo PreCheckFailure rather than throwing —
-		// FR-009 case (b) requires this repo to be marked failed without
-		// aborting the whole pre-check.
+		// record it as a per-repo PreCheckFailure rather than silently
+		// treating the repo as collision-free — FR-009 case (b) requires
+		// this repo to be marked failed without aborting the whole
+		// pre-check. `worktreeListDetailed` returns Result, not throws, so
+		// the error surfaces via result.ok rather than try/catch.
 		if (!worktreeCache.has(repoRoot)) {
-			try {
-				worktreeCache.set(repoRoot, await worktreeListDetailed(repoRoot))
-			} catch (error) {
-				const reason = error instanceof Error ? error.message : String(error)
+			const result = await worktreeListDetailed(repoRoot)
+			if (!result.ok) {
 				preCheckFailures.push({
 					repoName: plan.repo.name,
-					reason: `pre-check failed: ${reason}`,
+					reason: `pre-check failed: ${result.error}`,
 				})
 				failedRepoRoots.add(repoRoot)
 				continue
 			}
+			worktreeCache.set(repoRoot, result.value)
 		}
 		const entries = worktreeCache.get(repoRoot)!
 
@@ -327,9 +329,13 @@ async function isWorktreeHealthy(
 	}
 
 	// (c) Is the path listed in `git worktree list`?
-	const entries = await worktreeListDetailed(repoPath)
+	// If git fails (e.g. repo corrupted or binary missing), treat the
+	// worktree as unhealthy — the reconcile path will then retry via
+	// `git worktree add` which will surface the underlying error.
+	const result = await worktreeListDetailed(repoPath)
+	if (!result.ok) return false
 	const normalizedTarget = path.resolve(worktreePath)
-	return entries.some((entry) => path.resolve(entry.path) === normalizedTarget)
+	return result.value.some((entry) => path.resolve(entry.path) === normalizedTarget)
 }
 
 // =============================================================================