chore: archive 463 shipped changeset fragments before wiring render (#714)

CHANGELOG promotion was a manual operator step that was never run, so 463
fragments for work already shipped in <=1.3.1 accumulated in .changeset/.
Their notes were already hand-curated into the dated [1.2.0]/[1.3.0]/[1.3.1]
CHANGELOG sections (#690 backfill, PR #694). Rendering them now would
duplicate and mis-attribute shipped work.

Move them to .changeset/archived/ (read non-recursively by all changeset
tooling, so never rendered), keeping only the 3 genuinely-unreleased
fragments at the top level. Prep for wiring `render` into the release
finalize job (#690 follow-up).

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

.changeset/README.md

@@ -42,3 +42,7 @@ node scripts/changeset/cli.cjs render --version vX.Y.Z --date YYYY-MM-DD
 ```
 
 Reads every fragment, groups bullets by `type:`, replaces `## [Unreleased]` with a new `## [vX.Y.Z] - YYYY-MM-DD` block, opens a fresh `## [Unreleased]` above, deletes consumed fragments. Idempotent.
+
+## Archived fragments
+
+`.changeset/archived/` holds fragments for already-shipped releases (≤ 1.3.1), retained for provenance. Their content was hand-curated into the dated `## [1.x.y]` sections of `CHANGELOG.md` during the #690 backfill — they were never consumed by `render`. All changeset tooling enumerates `.changeset/` non-recursively, so archived fragments are never picked up or rendered. Do not move them back to the top level.