fix(#2736): write current_phase_name from the transition intent, not the lossy prose round-trip (#2821)

* fix(#2736): intent-first current_phase_name on transitions; dash-first prose precedence

Primary: completePhase (adapter) and beginPhase (via readModifyWriteStateMd
options) pass the intent-held display name to syncStateFrontmatter as an
authoritative override, applied after every derive/preserve/carry-forward
step — so the lossy prose round-trip can never destroy a name the transition
just resolved. Names containing a parenthetical
(`Closer-ruling measurement (D1a)`) now land in frontmatter verbatim instead
of collapsing to the parenthetical (`D1a`).

Secondary (#1695 AC #3 residual): parsePhaseFromProse prefers the em-dash
name when it is a genuine name (not a status keyword, not a `Milestone:`
tail), else falls back to the parenthetical — satisfying both first-party
writer shapes (`N — Name (aside)` and `N (Name) — EXECUTING`). Still lossy
for paren-containing names, which is why the intent-first override is the
primary fix.

plannedPhase carries no name in its intent, so it is naturally out of scope.

Fixes #2736

* docs(changeset): backfill PR number for #2736 fragment

* fix(#2736): drop an unnecessary type assertion on result.data

StateTransitionResult.data is already `Record<string, unknown> | undefined`,
so the cast was a no-op and tripped @typescript-eslint/no-unnecessary-type-
assertion (CI lint-tests red on the first push; every test lane was green).

---------

Co-authored-by: Tom Boucher <trekkie@nomorestars.com>

src/phase.cts

@@ -2456,7 +2456,15 @@ function cmdPhaseComplete(cwd: string, phaseNum: string, raw: boolean): void {
           planCount,
           summaryCount,
         );
-        stateContent = syncStateFrontmatter(stateContent, cwd);
+        // #2736: the transition holds the next phase's exact display name in
+        // the intent; pass it as authoritative so the sync's prose
+        // re-derivation cannot rewrite current_phase_name to the name's own
+        // parenthetical (`Closer-ruling measurement (D1a)` → `D1a`).
+        stateContent = syncStateFrontmatter(
+          stateContent,
+          cwd,
+          nextPhaseDisplayName ? { current_phase_name: nextPhaseDisplayName } : undefined,
+        );
 
         writes.push({ filePath: statePath, before: originalStateContent, after: stateContent });
       }