fix(dashboard): the duplicate banner judged the canonical by legacy lane ids (#3032)

Found by applying the check I proposed on #3028: **re-test each
`ALLOWED_OMISSIONS` entry — does the omission still fail once the excuse
is removed?** It found a stale excuse on its first run.

## The entry's blocker was never tested

```
"…TaskDetailModal.tsx::isNearDuplicateCanonicalInactive"
  reason: "…Correct supply needs a fetch — a data change. See the note at the site."
```

The reasoning gets the hard part right: passing `detailColumnFlags`
would answer about the **modal's** task, not the canonical, and would
type-check while reading as a conversion. Rejecting that is correct.

Then it concludes the seam needs a fetch — without checking what is in
scope.

- `columnFlagsByTaskId` is **already a prop of this component**
(declared `:367`, destructured `:727`, used for the fan-out map at
`:3718`), keyed by task id.
- The canonical is `tasks.find((c) => c.id === nearDuplicateOf)` — drawn
from the same loaded set the map covers. If the banner can render at
all, the canonical is in `tasks`.

So `columnFlagsByTaskId?.get(canonical.id)` is the canonical's own
flags, no fetch. **`Column.tsx:307` already does exactly this**, with a
comment making the same point about not reusing the row's flags — a
sibling call site of the same function, solved.

## What was broken

The banner's "this duplicates X" warning stayed up when the canonical
had landed in a **renamed** complete lane, because
`isNearDuplicateCanonicalInactive` fell back to the legacy ids and never
saw it as finished. Same user-visible symptom #2997 fixed for the card
chip; this is the modal.

## Verification

| state | result |
|---|---|
| clean | seams gate exit 0; 123/123 across `TaskDetailModal.rendering`
+ `Column.neardup-flags-arrival` |
| revert the supply | **gate exit 1** —
`isNearDuplicateCanonicalInactive() — supplied by 10/11 call sites;
omitted at TaskDetailModal.tsx:1 (of 2)` |

That mutation is the point: with the allow-list entry present, this
exact omission passed silently. It is now defended by the gate rather
than excused by it.

`tsc -p tsconfig.app.json` 0 errors in the file, lint clean, FNXC gate
exit 0.

## The general point

This is the second allow-list entry in two PRs whose stated blocker was
wrong — #3028 removed the other one (*"needs a published-API change"*;
the SDK is `private: true` and every consumer was in-repo).

An `ALLOWED_OMISSIONS` entry is a deferral **carrying a gate's
authority**. It reads as settled, it lives inside the checker, and it
turns "nobody tested this" into "someone tested it and concluded no". A
stale baseline *number* invites a recount; a stale *paragraph* invites
agreement. Both entries this gate carried were stale, and the note at
this call site had even been revised once — the revision corrected which
flags were wrong to pass, and left the untested "needs a fetch"
conclusion standing.

Worth a periodic sweep of the remaining entries as they accumulate; with
these two gone the list is empty, so the cheapest time to
institutionalise it is now.

---------

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

.changeset/detail-modal-canonical-flags.md

@@ -0,0 +1,7 @@
+---
+"@runfusion/fusion": patch
+---
+
+summary: The duplicate-warning banner in Task Detail now judges the canonical by its own lane, not the legacy ids.
+category: fix
+dev: `isNearDuplicateCanonicalInactive` in TaskDetailModal now receives `columnFlagsByTaskId.get(canonical.id)`; the allow-list entry claiming this needed a fetch is removed.

packages/dashboard/app/components/TaskDetailModal.tsx

@@ -944,15 +944,31 @@ export function TaskDetailContent({
   vs union confusion that `column-role-degraded-flags.test.ts` exists to catch, and it would type-check
   and read as a conversion.
 
-  Supplying it correctly needs the canonical's own resolved flags, which means fetching them: a data
+  FNXC:WorkflowResolvedColumns 2026-07-31-03:10 (the "needs a fetch" blocker was never tested):
-  change, out of scope here. So the omission is deliberate and is exempted BY CALL SITE rather than by
+  The paragraph above rejected passing `detailColumnFlags` — correctly, that would answer about the
-  function name, so core's sibling site stays guarded.
+  wrong task — and then concluded the seam needs a data change. It does not. `columnFlagsByTaskId` is
+  already a prop of this component (declared :367, destructured :727, used for the fan-out map), and
+  it is keyed by task id. The canonical is `tasks.find(c => c.id === nearDuplicateOf)`, so it is
+  drawn from the same loaded set the map covers — a `.get(canonical.id)` is the canonical's OWN
+  flags, with no fetch.
+
+  `Column.tsx:307` already does exactly this, with a comment making the same point about not reusing
+  the row's flags. The blocker was asserted from the shape of the problem (two different tasks) rather
+  than tested against what was in scope.
+
+  A canonical the map does not cover yields `undefined`, which is the documented legacy fallback —
+  strictly better than always-legacy, never a fabricated answer.
   */
   const showNearDuplicateWarning = Boolean(nearDuplicateOf)
     && workingTask.sourceMetadata?.nearDuplicateDismissed !== true
     && task.column !== "archived"
     && task.column !== "done"
-    && !isNearDuplicateCanonicalInactive(nearDuplicateCanonical);
+    && !isNearDuplicateCanonicalInactive(
+      nearDuplicateCanonical,
+      /* The CANONICAL's own flags, keyed by its id — never `detailColumnFlags`, which describes this
+         modal's task. Same shape as Column.tsx:307, the sibling site that already does this. */
+      nearDuplicateCanonical ? columnFlagsByTaskId?.get(nearDuplicateCanonical.id) : undefined,
+    );
   const [sourceAgent, setSourceAgent] = useState<Agent | null>(null);
   const [selectedSourceAgentId, setSelectedSourceAgentId] = useState<string | null>(null);
   const provenanceDisplay = getProvenanceLabel(workingTask, {

scripts/check-inert-flag-seams.mjs

@@ -150,12 +150,6 @@ const ALLOWED_OMISSIONS = new Map([
       + "change, not local wiring, which is the same 'needs a data change' category as the entry below. "
       + "Filed for the plugin-API owner rather than bodged here." },
   ],
-  [
-    "packages/dashboard/app/components/TaskDetailModal.tsx::isNearDuplicateCanonicalInactive",
-    { count: 1, reason: "The flags in scope describe the MODAL'S task; the canonical is a different task on a column this "
-      + "component never resolves. Passing them would type-check, read as a conversion, and answer "
-      + "about the wrong task. Correct supply needs a fetch — a data change. See the note at the site." },
-  ],
 ]);
 
 /*

scripts/lib/lane-wiring-baseline.json

@@ -10,7 +10,6 @@
     "packages/dashboard/src/routes/register-task-workflow-routes.ts": 1,
     "packages/dashboard/app/components/Lane.tsx": 1,
     "packages/dashboard/app/components/ListView.tsx": 1,
-    "packages/dashboard/app/components/TaskDetailModal.tsx": 1,
     "packages/dashboard/app/hooks/useBlockerFanout.ts": 1,
     "packages/cli/src/commands/dashboard-tui/app.tsx": 1,
     "packages/cli/src/commands/dashboard-tui/bucket-mapping.ts": 1,