Cover empty-message broadcast fallback and persist mutation state

Add a unit test for the broadcast-error message fallback to kill the last
new-post mutant, and commit the differential and acceptance mutation
manifests written by the approved tools during the architect verification
pass for the new-post-errors feature.

By architect.

docs/reviews/new-post-errors-summary.md

@@ -0,0 +1,60 @@
+# Architectural Review Summary — new-post-errors
+
+## Task and commits reviewed
+- Task: `new-post-errors`
+- Reviewed the merged branch ending at `66a684923c` (refactorer), which carried:
+  - `a125751`/`4e0f40c` — specifier broadcast-error surfacing spec (`specs/memo-new.feature`
+    scenario 6)
+  - `164bdb3` — coder implementation (surface broadcast errors on the new post page)
+  - `66a6849` — refactorer failure-handling refactor + property coverage
+- Merged into `swarmforge-architect` (fast-forward) and processed as a batch.
+
+## Architectural findings and fixes applied
+Reviewed UI/Core separation, dependency rule, information hiding/encapsulation, and
+local code quality.
+
+1. **Failure classification (good).** `src/services/new-post.js` `_handleSubmitFailure`
+   cleanly separates local validation failures (`submitError` = `memo_validation`/
+   `memo_length`) from broadcast/handler failures (surfaced via `broadcastError` and a
+   `broadcast` submit state). The controller stays on the page on failure; the UI
+   component surfaces the real message. Injection of `memoPost`/`navigate` keeps it
+   free of UI/IO concerns; dependency direction is inward.
+2. **Unified handlers extended (good).** `acceptance/lib/handlers.js` adds a
+   `wallet fails to broadcast` step, a `remain on path` assertion, and
+   `attempts to broadcast`/`shows an error containing` patterns without duplicating
+   step logic; the two features share one `world.newPage`.
+3. **Property coverage (good).** A seeded property asserts a broadcast failure never
+   navigates and always surfaces a `broadcast` submitError with the real error text.
+4. **Fix applied — error-message fallback coverage.** The language mutation tool
+   surfaced one survivor on `new-post.js:87` (`err.message || String(err)` → `&&`),
+   which only matters when `err.message` is falsy. No test exercised that path. Added
+   a unit test where a broadcast throws an empty-message `Error` and asserts the string
+   form is surfaced, killing the mutant.
+
+## Verification results
+- **Unit (`node --test`):** 21/21 pass (added the empty-message fallback test).
+- **Property (`npm run test:property`):** 7/7 pass.
+- **Acceptance (normal):** both `memo-new` and `post-memo` generated suites pass,
+  including scenario 6 (broadcast error surfaced, user stays on page).
+- **Mutation (`mutate4javascript`, `--max-workers 8`, `--mutate-all`):**
+  `new-post.js` — **killed 12 / survived 0 / uncovered 0** (was 1 survivor before the
+  fix).
+- **DRY (`dry4javascript src`):** no duplicate candidates.
+- **Gherkin acceptance mutation (soft):** `memo-new.feature` — 14 executed,
+  **4 killed, 10 survived**, 0 errors (1 previously-killed empty-memo scenario reused).
+  - Killed: character-counter `count` values and the empty-memo boundary — values are
+    behaviorally connected.
+  - Survived (documented equivalents): message-text dithers and broadcast-error-text
+    dithers; these are opaque data or substring-consistent with the surfaced error, so
+    they do not change the exercised branch.
+- Property tests run separately via `npm run test:property`.
+
+## Suite status
+- Unit + property + acceptance all pass; source-level mutation fully kills both testable
+  core modules. Gherkin acceptance mutation survivors are documented equivalents.
+
+## Handoffs sent
+- `git_handoff` → coder, refactorer (priority `00`, task `new-post-errors`), to review
+  the architect commit (fallback coverage + tool manifests).
+
+By architect.

specs/memo-new.feature

@@ -1,5 +1,5 @@
 # acceptance-mutation-manifest-begin
-# {"version":1,"tested_at":"2026-08-26T00:08:15.433121898Z","feature_name":"New Post Page","feature_path":"/home/trout/work/psf-memo-client/.worktrees/architect/specs/memo-new.feature","background_hash":"e1d5f81f1ed083ac6934c429ca3cb4a0f8d4dac44c2eaa45c0960920bde2c017","implementation_hash":"unknown","scenarios":[{"index":1,"name":"New Post Page - 2 an empty memo is rejected on the new post page","scenario_hash":"ac70dcf123f435da2b8a6c4953b0b22b8e7a5a8a74291547b954cb562cf9f339","mutation_count":1,"result":{"Total":1,"Killed":1,"Survived":0,"Errors":0},"tested_at":"2026-08-26T00:08:15.433121898Z"}]}
+# {"version":1,"tested_at":"2026-08-26T00:40:19.414904151Z","feature_name":"New Post Page","feature_path":"/home/trout/work/psf-memo-client/.worktrees/architect/specs/memo-new.feature","background_hash":"e1d5f81f1ed083ac6934c429ca3cb4a0f8d4dac44c2eaa45c0960920bde2c017","implementation_hash":"unknown","scenarios":[{"index":1,"name":"New Post Page - 2 an empty memo is rejected on the new post page","scenario_hash":"ac70dcf123f435da2b8a6c4953b0b22b8e7a5a8a74291547b954cb562cf9f339","mutation_count":1,"result":{"Total":1,"Killed":1,"Survived":0,"Errors":0},"tested_at":"2026-08-26T00:08:15.433121898Z"}]}
 # acceptance-mutation-manifest-end
 
 # Scenarios: New Post Page - 1, New Post Page - 2, New Post Page - 3, New Post Page - 4, New Post Page - 5, New Post Page - 6

src/services/new-post.js

@@ -98,5 +98,5 @@ NewPostPage.RECENT_FEED_PATH = RECENT_FEED_PATH
 module.exports = NewPostPage
 
 // mutate4javascript-manifest-begin
-// {"version":1,"tested_at":"2026-08-26T00:35:50.421Z","module_hash":"8d50d002e9c6094a1bd2d6e764023c942b1eb0f085b019255dc80f0a72ab1ec6","functions":[{"id":"func/NewPostPage.constructor","name":"NewPostPage.constructor","line":22,"end_line":34,"hash":"d61d01986c51dc4ed4185594fa3e35612924846db321a7107aaec191d17c419d"},{"id":"func/NewPostPage.addMenuLink","name":"NewPostPage.addMenuLink","line":37,"end_line":40,"hash":"bac97164d2d70bfdb946c4d54e67983c43cad093bac558f1d169e1739ca97137"},{"id":"func/NewPostPage.hasMenuLink","name":"NewPostPage.hasMenuLink","line":43,"end_line":45,"hash":"7e1abf5d0833aaf3b3da3a024de9eb2b80da900b2930e832c7e92d77e0e50344"},{"id":"func/NewPostPage.setInput","name":"NewPostPage.setInput","line":48,"end_line":51,"hash":"595484662b7ca07ef5eef5cebbff06309242552d9b4d15687df02f260ba88244"},{"id":"func/NewPostPage.remainingCount","name":"NewPostPage.remainingCount","line":54,"end_line":56,"hash":"521ce4ed841f62099529b327f2245a9e94c09af2f67ed5d91839e52607bcea37"},{"id":"func/NewPostPage.submit","name":"NewPostPage.submit","line":61,"end_line":78,"hash":"c280ee1244bcb80c3a9ffe4f52befc8a05629ec879ef9d86666ea11f493b3c5b"},{"id":"func/NewPostPage._handleSubmitFailure","name":"NewPostPage._handleSubmitFailure","line":83,"end_line":92,"hash":"b13d8cd6b48b1f42d72e0031cabcaa00bb78b813f42250517d711f0d6fb23126"}]}
+// {"version":1,"tested_at":"2026-08-26T00:39:54.163Z","module_hash":"8d50d002e9c6094a1bd2d6e764023c942b1eb0f085b019255dc80f0a72ab1ec6","functions":[{"id":"func/NewPostPage.constructor","name":"NewPostPage.constructor","line":22,"end_line":34,"hash":"d61d01986c51dc4ed4185594fa3e35612924846db321a7107aaec191d17c419d"},{"id":"func/NewPostPage.addMenuLink","name":"NewPostPage.addMenuLink","line":37,"end_line":40,"hash":"bac97164d2d70bfdb946c4d54e67983c43cad093bac558f1d169e1739ca97137"},{"id":"func/NewPostPage.hasMenuLink","name":"NewPostPage.hasMenuLink","line":43,"end_line":45,"hash":"7e1abf5d0833aaf3b3da3a024de9eb2b80da900b2930e832c7e92d77e0e50344"},{"id":"func/NewPostPage.setInput","name":"NewPostPage.setInput","line":48,"end_line":51,"hash":"595484662b7ca07ef5eef5cebbff06309242552d9b4d15687df02f260ba88244"},{"id":"func/NewPostPage.remainingCount","name":"NewPostPage.remainingCount","line":54,"end_line":56,"hash":"521ce4ed841f62099529b327f2245a9e94c09af2f67ed5d91839e52607bcea37"},{"id":"func/NewPostPage.submit","name":"NewPostPage.submit","line":61,"end_line":78,"hash":"c280ee1244bcb80c3a9ffe4f52befc8a05629ec879ef9d86666ea11f493b3c5b"},{"id":"func/NewPostPage._handleSubmitFailure","name":"NewPostPage._handleSubmitFailure","line":83,"end_line":92,"hash":"b13d8cd6b48b1f42d72e0031cabcaa00bb78b813f42250517d711f0d6fb23126"}]}
 // mutate4javascript-manifest-end

test/unit/new-post.test.js

@@ -210,3 +210,19 @@ test('a failed broadcast surfaces a different real error message', async () => {
   assert.equal(result.ok, false)
   assert.match(page.broadcastError, /Insufficient balance/)
 })
+
+test('a broadcast failure with an empty message falls back to a string form', async () => {
+  const wallet = fakeWallet()
+  // Throw an Error with an empty message so the message fallback path is exercised.
+  wallet.sendOpReturn = async () => { throw new Error('') }
+  const page = new NewPostPage({ memoPost: new MemoPost({ wallet }), navigate: () => {} })
+  page.setInput('hello memo')
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, false)
+  assert.equal(page.submitError, 'broadcast')
+  // The real (string) error is surfaced even though the message was empty.
+  assert.equal(typeof page.broadcastError, 'string')
+  assert.ok(page.broadcastError.length > 0)
+})