Give the reviewed change a path to the human

The completion tail ended at TaskCompleted with no pull request. Nothing in
the running system ever called the review or submission endpoints: the whole
event log holds zero ReviewRecorded and zero TaskSubmitted, so the merge
reflection, the publisher and the human trust boundary had no entry point.

Four links, in the order the tail needs them:

- finalize commits first and runs the quality gate against the committed
  tree, so the gate result is bound to the commit being submitted.
  CheckSubmission requires gate sha, review sha and head sha to be one
  commit, which a gate run on the pre-commit tree can never satisfy.
- The worker seals the reviewer's findings and submits, through a new
  /v1/federation/workers/<id>/submit. A blocking review returns the task to
  implementation instead; a project with no forge still completes directly.
- The reviewing session is told where findings go. The brief asked for
  findings and named no file, and it described a diff nobody supplied.
- GiteaPublisher.Push asks the forge what the branch holds before reaching
  for a local checkout. A worker-owned worktree is on another machine and
  has already pushed the commit; the coordinator has no such directory.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CVbaKucEYBjMqVeUgJUsc1

internal/review/review.go

@@ -165,7 +165,11 @@ func Decode(b []byte) (Result, error) {
 // Instructions is the reviewer's whole brief. It is narrow on purpose: an open
 // invitation produces a list of ways the reviewer would have written it
 // instead, which is not review.
-const Instructions = `Review the supplied diff against, in order:
+// The diff is named rather than supplied: nothing populates agentctx.Evidence
+// on the federated path, so a brief that said "the supplied diff" described
+// material the reviewing session never received.
+const Instructions = `Read the change under review with git in this worktree,
+then review it against, in order:
 1. the task goal and acceptance criteria
 2. the human decisions and constraints
 3. the repository rules
@@ -180,4 +184,17 @@ defect or contradicts a decision, minor otherwise.
 
 Do not redesign the solution. Do not suggest optional refactors. Do not edit
 any file. Do not report style preferences unless they violate a repository
-rule. You are not implementing this task and you do not decide its lifecycle.`
+rule. You are not implementing this task and you do not decide its lifecycle.
+
+Write your findings to .orchestra/review.json before you finish, even when you
+found nothing:
+
+    {"findings": [
+      {"id": "f1", "severity": "blocker", "file": "path/to/file.go",
+       "line": 42, "claim": "what is wrong", "evidence": "why, from the diff"}
+    ]}
+
+An empty findings list is how you report a clean review. Do not set a commit
+sha: Orchestra binds the review to the commit it seals, because the commit is
+not something you can observe. A review with no file is a review nobody can
+act on, so the file is what finishes the phase, not the text in your pane.`