feat: ceremony flips to grouped — changelog.d/shape = grouped, five fragments converted, docs per D6

167/175 gain '### Added', 173/178 '### Changed', 180 '### Fixed' — every
bullet byte-identical, headings only (the #158 bar, inverted). CONSUMERS.md
names the sentinel and the flip procedure; changelog.d/README.md names the
sentinel. 182.md is this PR's own fragment, grouped atop the sentinel it
ships.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

changelog.d/167.md

@@ -1,3 +1,5 @@
+### Added
+
 - `changelog_fragment_problem` bounds every entry at 300 normalized
   characters, red on the PR that writes the fragment; the armed guard and
   the assembler inherit the one definition (#167).

changelog.d/173.md

@@ -1 +1,3 @@
+### Changed
+
 - Private-repository label callers document `actions: read` alongside checks and statuses for workflow-run check-rollup nodes (#173).

changelog.d/175.md

@@ -1 +1,3 @@
+### Added
+
 - Add `post-merge` issue state for merged `Refs` work awaiting triage-owned verification.

changelog.d/178.md

@@ -1,3 +1,5 @@
+### Changed
+
 - BUILDER.md: a park declaration stands until its facts change — a
   nothing-changed resumption posts nothing; only a no-open-PR park owes a
   refresh, inside the 48-hour reclaim window (#178).

changelog.d/180.md

@@ -1,3 +1,5 @@
+### Fixed
+
 - `decide_state()` refuses `state:needs-human` while the hand-set `blocked`
   label stands — the PR falls to `state:addressing`, exactly parallel to the
   `needs-ruling` exclusion; never emitted by `blockers()` (#180).

changelog.d/182.md

@@ -0,0 +1,10 @@
+### Added
+
+- `changelog.d/shape` — an optional one-line sentinel, `flat` or `grouped`,
+  that pins the fragment set's shape and outranks the newest-published-section
+  inference; absent, the inference binds unchanged (#182).
+
+### Changed
+
+- Ceremony's changelog is grouped from this release forward: the pending
+  fragments carry `### ` headings under a `grouped` sentinel (#182).

changelog.d/README.md

@@ -7,4 +7,5 @@ published, nothing else — and the release PR folds them all into the next
 filenames never conflict, which is this directory's whole reason to exist.
 This README is the marker that keeps the directory tracked when it holds no
 fragments (#112 D1) — `changelog-armed` refuses a tree without it; do not
-delete it.
+delete it. The `shape` sentinel beside it declares the set's shape —
+`grouped` here, so every fragment carries `### ` headings (#182).

changelog.d/shape

@@ -0,0 +1 @@
+grouped

docs/CONSUMERS.md

@@ -480,7 +480,13 @@ CONTRIBUTING may sharpen it, but this is the floor the guards assume:
   kind. A repo is grouped or flat, never both (#112 D4). The assembler
   merges groups in canonical order — Added, Changed, Fixed, Removed,
   Deprecated, Security, then anything else first-seen — and inside a
-  group entries read newest issue first (#112 D5).
+  group entries read newest issue first (#112 D5). Which shape binds is
+  inferred from the newest published section, unless an optional sentinel
+  `changelog.d/shape` — one line, exactly `flat` or `grouped` — declares
+  it and outranks the inference (#182). To flip a repo's shape, land one
+  PR that adds the sentinel and converts every pending fragment to the
+  declared shape, bullets byte-identical; the sentinel stays after the
+  release, as the declaration a reader in the directory finds.
 - **One line: say what changed, and stop.** Lead with the surface, not
   the mechanism — "`state:needs-human` is set at handoff" beats "the
   labels workflow now also wakes on `labeled`". The why and the how