fix(#4134): refuse punctuation-only milestone heading names (#4358)

* test(#4134): fail-first regression — refuse punctuation-fragment milestone names

A first-milestone ROADMAP.md H1 that puts the version after the name
(# Roadmap: Project — Name (v1.13)) leaves exactly ')' after the heading's
own version token, which the ADR-3180 §7.2 pinned name rule returns as a
COMPLETE-scope milestone name. Failing-first coverage:

- getMilestoneInfo: name-then-version H1 (STATE-anchored + ROADMAP-only
  fallback) must yield TRUNCATED {version, name: null}, never ')'
- the refusal is level-agnostic (H2/H3)
- punctuation-family remainders (')', '()', '**', '.,;:', ']}', emoji-only)
- listMilestoneHeadings enumerates the heading with name: null
- init manager CLI reports milestone_name: null and no lone ')' anywhere
- property (seed 20260905, 300 runs): a word-char remainder is always a
  name, a punctuation-only remainder never is
- negative space: canonical delimiter forms, parenthetical names (#3171),
  trailing markers, digit-only names, CRLF headings, version-last-no-parens
  control

* fix(#4134): refuse punctuation-only milestone heading names

extractMilestoneHeadingName returns everything after the heading's own
version token as the name (ADR-3180 §7.2 pinned rule), which assumes
version-then-name. A name-then-version heading — the H1 a first-ever
ROADMAP.md drifts into ('# Roadmap: Project — Name (v1.13)') — leaves
exactly ')' after the token, and that fragment was returned as a
COMPLETE-scope milestone name, propagating into init.* JSON output and
buildStateFrontmatter's STATE.md writes.

A remainder with no letter or digit anywhere (any script) is heading
structure, not a curated name: refuse it as name: null so callers report
the honest §7.2 rule-6 answer (version kept, TRUNCATED scope). Names
that merely contain punctuation are unaffected — '(' stays an ordinary
name character (#3171) — and digit-only names qualify.

Also closes the template gap that lets the shape occur: the roadmapper
agent's output_formats now templates the version-free canonical H1
('# Roadmap: [Project Name]', per templates/roadmap.md) instead of
leaving a first milestone's title line to invention. The new section
shifts the file's existing bare-gsd-tools prose mention from line 647
to 660, so its line-keyed PROSE_ALLOWLIST entry moves with it.

Emitted-Drift-Ack-Growth: gsd-roadmapper.md — deliberate +498 bytes: new '### 0. Top-Level Title (H1)' output_formats section templating the canonical version-free H1, closing the first-milestone template gap that lets an H1 drift into 'Name (vX.Y)' and corrupt milestone_name extraction (#4134)

* chore(#4134): add changeset

* chore(#4134): backfill PR number in changeset

---------

Co-authored-by: sim <sim@local>

agents/gsd-roadmapper.md

@@ -331,6 +331,19 @@ After roadmap creation, REQUIREMENTS.md gets updated with phase mappings:
 
 **CRITICAL: ROADMAP.md requires TWO phase representations. Both are mandatory.**
 
+### 0. Top-Level Title (H1)
+
+The H1 carries the PROJECT name only — never a version and never a milestone name:
+
+```markdown
+# Roadmap: [Project Name]
+```
+
+Milestone identity (version + name) lives in milestone headings (`## vX.Y — [Name]`) or
+`## Milestones` bullets (`🚧 **vX.Y [Name]**`), never in the H1. A trailing version in the
+H1 (`# Roadmap: [Project] — [Name] (vX.Y)`) corrupts milestone-name extraction (#4134).
+`~/.claude/gsd-core/templates/roadmap.md` is the canonical shape.
+
 ### 1. Summary Checklist (under `## Phases`)
 
 Use the form matching `phase_id_convention` from config.