Normalize Extensions v2 contract

[admdly]

Breaking-within-v2 contract tidy. No D1 migration; coordinated release with the site PR (FOSSBilling/extensions#343, same branch name).

What changed

• Cursor pagination everywhere: GET /developers, GET /developers/claims, GET /developers/{id}/history move from offset to keyset cursors (PaginationSchema); offset helpers deleted. Same-second ties still broken by rowid.
• GET /developers?scope=all|unapproved (?status= kept as deprecated alias, 422 on explicit conflict); scope=pending + disagreeing status now 422 instead of silently ignored.
• New POST /extensions/{id}/relist (+ relist() DB, extension-relisted mail, revalidate).
• Errors: statusFromOwnershipErrorCode folded into statusFromWriteErrorCode; shared NotifiedSchema fragment; tags by resource (listDevelopers, claim decisions → Developers).
• New contract.test.ts (static-beats-param, reserved ids, scope-misuse matrix, cursor envelopes).
• README + AGENTS.md updated (relist, scope, cursor pagination, bot [auto] note convention).

Follow-up (deferred, builds on this): #251 moderator content-correction.

Testing

• npm run typecheck, lint (0 errors), format:check clean.
• test/services/extensions/v2/: 11 files / 321 tests pass, incl. new relist, scope/cursor, and contract coverage.

No config/binding changes.

[cubic-dev-ai]

Review completed against the latest diff

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[cubic-dev-ai]

All reported issues were addressed across 16 files

<sub>Requires human review: Auto-approval blocked because this review re-detected 3 unresolved issues already reported by Cubic.

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[cubic-dev-ai]

1 issue found across 9 files (changes from recent commits).

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Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="src/services/extensions/v2/db/developer-claims.ts">

<violation number="1" location="src/services/extensions/v2/db/developer-claims.ts:312">
P3: The `scope=mine` cursor is bound only to scope, not to the claimant, even though `claimantId` is the primary filter of that result set. A cursor minted by one user, passed with another user's `scope=mine` request, decodes cleanly and seeks from the first claimant's key boundary, silently skipping the second claimant's newest claims — the same "wrong key boundary" page this PR rejects for scope and history. In contrast, the `listHistory` binding added in this same delta tags the developer id (`d`) and rejects a foreign one. Tag the claimant id for `scope=mine` and validate it on decode, mirroring `decoded.d` in `listHistory`.</violation>
</file>

[cubic-dev-ai]

All reported issues were addressed across 6 files (changes from recent commits).

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[cubic-dev-ai]

0 issues found across 1 file (changes from recent commits).

<sub>Requires human review: This PR introduces a breaking public API contract change and coordinated site migration that requires human sign-off.

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