Threads, commands and labels on the new loop (M2.3)

- Commands that name their item ("go #14", "abandon #14", "stop #14")
  apply to it wherever they're said; go, approve and abandon alone at top
  level are asked about (L5). stop is never taken as an answer.
- A plain-language reply to a restatement is read by GoAheadReader, one
  model call that agrees only on a clear yes; questions never reach it. The
  agent says "taking that as a go-ahead on rev-N" first, bound to the
  revision on screen at arrival (L3, L5, D1).
- Labels steer (D1): `bug` goes ahead after tuning.loop.bug_grace_s
  (default 600 s) unless the operator replies; `discuss` isn't offered
  restate until the operator has spoken; `bug`, `discuss` and `design` add
  to the driver's instructions. A restatement asks no questions.

Tests: label and command unit tests, the property walk with labelled
issues, plain yeses, named gos and time passing (grace_only_unanswered,
discuss_talks_first), and e2e tests for a bug proceeding after its grace
period and a plain-language go-ahead.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

docs/Tuning-Guide.md

@@ -513,3 +513,16 @@ Later work that will add knobs, each with its own section here:
   model and a policy for what is safe to summarize.
 - **Benchmarking the other roles:** planner and delegate, with delegation
   turned back on for comparisons across frontier tiers.
+
+### `tuning.loop.bug_grace_s` — default 600
+
+How long the restatement of an issue labelled `bug` waits for a reply before
+the agent goes ahead on its own (architecture D1). Any reply in the item's
+thread stops the countdown, and `go` starts at once.
+
+- **Too low:** you can't read the restatement before the fix starts, so a
+  misread report costs a wasted milestone.
+- **Too high:** bugs wait as long as features, and the label buys nothing.
+- **Deciding:** about the time it takes you to notice a message and read it
+  when you're around. A wrong start costs only time, since the fix still comes
+  as a PR you review.