feat(core): declarative migrations, so content queries span a family's versions

[cuibonobo]

Summary

Closes #448.

• Declared steps replace the function form. migration(from, to, [rename, map, add, drop, derive]) builds migrate() from the steps and keeps them on the Migration. It checks them against both handles' schemas at construction: a step naming a field that isn't there, a carried field the target would refuse, or a required field nothing produces throws StackMigrationError. derive is the one opaque step (type changes, splits, computed values); its output is still validated at write time.
• A collection's content filter or sort now spans older versions. Core composes each older version's steps into field origins and rewrites the query per version: rename and add translate; map translates filters (not sorts); derive narrows. Narrowed versions set skipped.older as feat(core): type a collection's content filters and sorts from its content type #447 did; newer versions stay out of reach.
• Two wire shapes: filter.contentByType (a flat content arm per typeId) and sort.contentFieldByType ({ field } or a pre-reduced { value } per typeId). Each is gated by a capability that is a cap on keys; 0 declines it, and the collection falls back to feat(core): type a collection's content filters and sorts from its content type #447's narrowing. Local adapters declare 64.
• Implemented in MemoryAdapter, sqlite-shared (both SQLite adapters), parseQueryBody(), normalizeCapabilities(); adapter-api carries both in the POST body unchanged.

Spec

• docs/spec/data-model.md — new § Migration steps, § Content queries across versions, § Content by type; § Type migrations, § Type handles, § Sorting and pagination, § Sorting by a content field, § Capability-gated filters updated.
• docs/spec/adapters.md § Adapter capabilities — the two caps and the local-required rule.
• docs/spec/wire-format.md — discovery example, § Records (body-only shapes and their 400s), § Bounding query cost.
• Small wording updates in apps.md and versioning.md ("migrations", not "migration functions").

Verification

All six from AGENTS.md pass locally: format:check, check:refs, lint, test (3,209 tests), build, typecheck.

New coverage: step construction checks and origin composition (type-handle, migration-steps tests); collection translation across rename/map/add/derive, a three-version chain, pagination under a translated sort, cap fallback and hand-built migrations, on Stack and ScopedStack; validation of both shapes; conformance-suite cases for both shapes (pass on MemoryAdapter and native SQLite); wire fixtures for both shapes and two bad_request cases.

Notes for reviewers

• Sort key spelling: a separate sort.contentFieldByType mirroring the filter, rather than overloading contentField with a map — every reader of contentField treats it as a string.
• Empty arms are allowed ({} matches every record at that typeId, no wider than typeId alone); an empty map is refused. An add constant that matches a filter needs this.
• map keeps unlisted values, so map('status', { done: 'finished' }) has two v1 sources for 'finished'. The arm asks for 'done'; the first page probes for the other source and sets skipped.older on a match, rather than narrowing the issue's headline case. A second such key in one arm narrows.
• Migration now requires steps; one built by hand has no origins and is narrowed.

🤖 Generated with Claude Code

https://claude.ai/code/session_01LREkawquacdfohXcxKRYWa

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Generated by Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: a40cee0

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 11 packages

Name	Type
@haverstack/core	Minor
@haverstack/wire-types	Minor
@haverstack/conformance-fixtures	Minor
@haverstack/adapter-conformance	Minor
@haverstack/record-adapter-sqlite	Minor
@haverstack/record-adapter-do-sqlite	Minor
@haverstack/adapter-api	Patch
@haverstack/adapter-local	Patch
@haverstack/blob-adapter-disk	Patch
@haverstack/blob-adapter-s3	Patch
@haverstack/commons	Patch

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