Add posting-state coverage and persist mutation state

Cover the new-post posting flag (initial idle, in-flight true, settled
false) to kill the four surviving mutants, and commit the differential and
acceptance mutation manifests written by the approved tools during the
architect verification pass for the new-post-page feature.

By architect.

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

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+# Architectural Review Summary — new-post-page
+
+## Task and commits reviewed
+- Task: `new-post-page`
+- Reviewed the merged branch ending at `d57975c466` (refactorer), which carried:
+  - `9385034`/`4fa92d1` — specifier New Post Page Gherkin spec (`specs/memo-new.feature`)
+  - `05f393c` — coder implementation (`src/services/new-post.js`, page wiring)
+  - `d57975c` — refactorer property tests for memo post / new post invariants
+- 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. **Testable controller behind adapters (good).** `src/services/new-post.js` is a
+   testable controller wrapping `memo-post.js`; it holds draft input, the remaining-
+   character counter, typed validation/length errors, and feed navigation. `memoPost`
+   and `navigate` are injected so the module stays free of UI/IO concerns. Dependency
+   direction is inward.
+2. **Unified acceptance handlers (good).** `acceptance/lib/handlers.js` now drives both
+   `post-memo.feature` and `memo-new.feature` through one `world.newPage`, reusing the
+   shared Memo post behavior. Wording differences are normalized via shared regex
+   alternations; no step logic is duplicated.
+3. **Property tests (good).** `test/property/{harness,memo-post.property.test}.js`
+   assert seeded invariants (validation classification across the length boundary,
+   counter conservation `remaining === MAX - len`, `setInput` round-trip, menu-link
+   idempotence). Kept separate from unit tests as the architecture requires.
+4. **Fix applied — posting-state coverage.** The language mutation tool surfaced 4
+   survivors in `new-post.js`, all around the `posting` state flag (initial value and
+   its true/false transitions in `submit`). Added unit coverage asserting the page
+   starts idle, is `posting=true` while a submit is in flight (via a deferred wallet),
+   and returns to `posting=false` on success and on error. This killed all 4 survivors.
+
+## Verification results
+- **Unit (`node --test`):** 18/18 pass (added 2 posting-state tests).
+- **Property (`npm run test:property`):** 6/6 pass.
+- **Acceptance (normal):** both `memo-new` and `post-memo` generated suites pass.
+- **Mutation (`mutate4javascript`, `--max-workers 8`):**
+  - `memo-post.js`: differential reuse (module unchanged since its 7/7 kill).
+  - `new-post.js`: after coverage fix, **killed 11 / survived 0 / uncovered 0**
+    (was 4 survivors before the fix).
+- **DRY (`dry4javascript src`):** no duplicate candidates.
+- **Gherkin acceptance mutation (soft):**
+  - `memo-new.feature`: 11 executed — **5 killed, 6 survived**, 0 errors.
+    - Killed: empty-memo boundary; character-counter `count` example values (217/212/0)
+      — proving those values are connected to behavior.
+    - Survived (documented equivalents): message-content dithers (4) plus case/length-
+      neutral dithers in the counter scenario — message text is opaque data; only length
+      affects the counter, so these don't change observable behavior.
+  - `post-memo.feature`: empty-memo scenario reused as killed; remaining 5 executed are
+    the same documented message-content equivalents.
+- 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-page`), to review the
+  architect commit (posting-state coverage + tool manifests).
+
+By architect.