Phase 7c: pagination #81

Summary

Implement phase 7c, pagination, per the design docs/work/mvp/phase7/phase7c/2026-10-09-phase7c-pagination-design.md and the plan docs/work/mvp/phase7/phase7c/2026-10-09-phase7c-pagination.md.

Scope (36 rows)

PAGE-1–PAGE-36 (33 built, 3 N/A). One feat! PR, grouped as:

1. Internal: QuerySplice (case-sensitive, with property tests), LinkHeaderParser with its vector, LinkTarget.TryResolve.
2. IPageStrategy<TPage,T>, Page<T>.Request, the built-in strategies and PaginationStrategies factories, single-use enumerables, the one fetch-and-parse step, the async cutover (AsyncPageable<T>, Pageable.Create), the blocking Pageable<T> / CreateBlocking, the lifecycle suite, architecture tests and the Link-origin Security class.
3. FetchedPage<T>, PagingOptions, Pageable.FromFetchers (PAGE-34, PAGE-35); loopback wire tests; AOT smoke (paged round trip); docs/sdk-documentation/pagination.md; checklist, CHANGELOG, corrections, roadmap status note.

Breaking changes

1. Pageable.Create takes IAsyncHttpClient, an IPageStrategy<TPage,T> and RequestOptions?.
2. PaginationStrategies.* gain the item selector and a second type parameter; Cursor defaults to "cursor"; PageNumber loses hasMore and gains startPage; LinkHeader loses rel and gains headerName and allowCrossOrigin.
3. PageNumber ends on an empty page (PAGE-17).
4. LinkHeader ends on a cross-origin or invalid target, strips userinfo, reads every Link instance, resolves against the response URL.
5. The splice matches names case-sensitively and drops duplicates.
6. AsPages() loses pageSizeHint, becomes non-virtual and single-use per view; subclasses override WalkPagesAsync.
7. Page<T>'s constructor requires the Request.
8. maxPages <= 0 and a non-replayable template body throw at construction.
9. A null envelope throws DeserializationException.

Open for the lead

• P7c-3: pageSizeHint removed from AsPages().
• P7c-6: per-call overrides are RequestOptions (removes a parameter type).
• P7c-12: cross-origin Link targets end the stream unless allowCrossOrigin: true.
• P7c-16: PagingOptions is a mutable class.

Done when

• Every plan task is done, the checklist has one row per requirement ID, and build, format, tests, coverage, AOT smoke, dependency audit and the housekeeping probe all pass.