Support exact secondary-root Agent worktrees

[nickdavis]

Summary

• authorize Agent worktree execution against the complete canonical saved-workspace root set, including exact worktrees for secondary repository roots
• keep saved-workspace identity separate from session worktree projection while failing closed for stale, unmatched, duplicate, or ambiguous root bindings
• preserve explicit secondary-repository selection through Agent start/explore paths and add direct create-session, bind, and builtin-review steer coverage

Validation

• make dev-test FILTER=AgentRunWorktreeStartTests — 55 tests passed
• make dev-lint
• make dev-swift-build PRODUCT=RepoPrompt
• .agents/skills/rpce-contribution-check/scripts/preflight.sh commit
• .agents/skills/rpce-contribution-check/scripts/preflight.sh push
• independent read-only review of origin/main..HEAD — no blockers

Additional validation context

The full local PR-ready root suite was attempted. It progressed through the affected coverage but did not complete: an unrelated durable-artifact concurrency test reported a busy publication result, and the run later stopped producing output in workspace-context tests. The focused Agent worktree suite, strict lint, and affected product build all passed.

[morluto]

Audit disposition — direct correctness blocker (2026-08-14)

The complete-root authorization and fail-closed handling of stale, duplicate, and ambiguous bindings are good. The no-binding Context Builder branch still violates the intended physical-root contract, however: it returns workspaceDirectoryPath rather than the selected executionPath. A request targeting a stored/secondary physical root can therefore fall back to the active/primary workspace directory.

Return the selected canonical physical root when no session binding overrides it, add a focused stored-versus-active workspace regression, and rerun the failing app shard. Treat the separate Codex context-window failure as a baseline/rebase issue if it is unrelated. I would not merge until the root-selection regression is fixed.

[morluto]

Deep-review assessment — 2026-08-14

Disposition: block on the no-binding execution-root regression. Authorizing bindings against the complete canonical workspace root set and rejecting stale/duplicate/ambiguous logical roots is the right model. However, ContextBuilderWorkspaceContext returns workspaceDirectoryPath when bindings is empty, even though the selected physical executionPath should remain authoritative. In a multi-root or inactive/stored selection this can route Context Builder back to the active/primary workspace.

Return the selected canonical physical execution root in the no-binding branch and add a regression where the selected secondary/stored workspace differs from the active primary workspace. This aligns with the reviewed exact-head shard failure that observed the active workspace instead of the stored selection. Rerun the failing shard and the full AgentRunWorktreeStartTests after the fix.