fix(webui): repair traffic live path contracts for #640 review

Address PR #885 REQUEST_CHANGES: full head_sha pins from queue signals,
reviewer leases keyed by pr_number only, claim inventory via entries,
live-path fixture tests, and traffic state vocabulary docs.

Closes #640 (re-review at new head)

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

webui/queue_loader.py

@@ -4,7 +4,7 @@ from __future__ import annotations
 
 import os
 import re
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 from datetime import datetime, timezone
 from typing import Any, Callable
 from urllib.parse import urlparse
@@ -31,10 +31,20 @@ class PaginationMeta:
 
 @dataclass(frozen=True)
 class QueueItem:
+    """One queue row.
+
+    ``extra`` holds *display* strings for the queue page (values are truncated
+    or humanized for rendering). ``signals`` holds the *authoritative* typed
+    values taken straight from the Gitea payload, for consumers that classify
+    or pin state rather than render it (#640). Never derive identity or
+    concurrency decisions from ``extra``.
+    """
+
     number: int
     title: str
     badges: tuple[str, ...]
     extra: dict[str, str]
+    signals: dict[str, Any] = field(default_factory=dict)
 
 
 @dataclass(frozen=True)
@@ -134,21 +144,37 @@ def _format_pr_item(pr: dict, badges: tuple[str, ...]) -> QueueItem:
         "mergeable" if mergeable is True else "conflicted" if mergeable is False else "unknown"
     )
     linked = _extract_linked_issue(pr.get("title"), pr.get("body"))
+    head_sha = str(head.get("sha") or "")
+    labels = tuple(
+        str(lb.get("name") or "") for lb in (pr.get("labels") or []) if lb.get("name")
+    )
     return QueueItem(
         number=int(pr["number"]),
         title=str(pr.get("title") or ""),
         badges=badges,
         extra={
             "branch": f"{head.get('ref', '?')} → {base.get('ref', '?')}",
-            "head_sha": str(head.get("sha") or "")[:12],
+            # Display only — truncated. Pin against signals["head_sha"] instead.
+            "head_sha": head_sha[:12],
             "mergeable": merge_label,
             "linked_issue": str(linked) if linked is not None else "",
         },
+        signals={
+            "head_sha": head_sha,
+            "head_ref": str(head.get("ref") or ""),
+            "base_ref": str(base.get("ref") or ""),
+            "mergeable": mergeable if isinstance(mergeable, bool) else None,
+            "labels": labels,
+            "linked_issue": linked,
+        },
     )
 
 
 def _format_issue_item(issue: dict, badges: tuple[str, ...]) -> QueueItem:
-    labels = ", ".join(lb.get("name", "") for lb in issue.get("labels", []))
+    label_names = tuple(
+        str(lb.get("name") or "") for lb in (issue.get("labels") or []) if lb.get("name")
+    )
+    labels = ", ".join(label_names)
     assignee = (issue.get("assignee") or {}).get("login", "")
     return QueueItem(
         number=int(issue["number"]),
@@ -159,6 +185,11 @@ def _format_issue_item(issue: dict, badges: tuple[str, ...]) -> QueueItem:
             "assignee": assignee or "unassigned",
             "state": str(issue.get("state") or ""),
         },
+        signals={
+            "labels": label_names,
+            "assignee": assignee,
+            "state": str(issue.get("state") or ""),
+        },
     )