feat: cursor lists by inclusion, page sequences, and the beta-19425 pin

[Blind-Striker]

What

Three commits, each green on the Windows matrix (net472, net8.0, net9.0, net10.0, live lane included):

1. Cursor lists bind by inclusion; Enumerate*Async returns CursorSequence<TPage, TItem>. A query that carries limit, order, and cursor derives from ListRequest whatever filters it declares beside them; a continuation is the first request again with order dropped and the returned cursor in place, so every filter rides every page. SessionsClient.EnumerateSessionsAsync appears. The sequence still enumerates as IAsyncEnumerable<TItem> and exposes the generated page envelopes through Pages. ADR-0017, the protocol and runtime canon, and CONTEXT.md are revised; the pagination guide is rewritten. Increment benchmark on the pagination ladder: 394,048 → 394,544 allocated bytes over a three-page, thirty-item walk (+496 B); the manual-paging control is unchanged.
2. SourceLink 10.0.303. Microsoft.Build.Tasks.Git 10.0.301 carries GHSA-23fw-v26w-5fgq (CVE-2026-62900, published 2026-09-08); a cold restore reports NU1902 and the analyzer wall turns it into an error.
3. Accepted snapshot → 20aff6d9f643afe9abf8a048e68f019d049f5329, upstream's beta branch head, shipped as @opencode/cli@0.0.0-beta-19425. v2.session.messageUpdate leaves the surface (upstream removed the message content mutation API in refactor(session): remove message content mutation API anomalyco/opencode#48043) together with the ISessionMessageAssistant union only its body used; session.message.content.updated leaves the live event union; the message list gains its type filter; provider/model records gain websocket, compaction records cost/tokens. README, spec/SNAPSHOT.md, the roadmap, and ADR-0005 now name the @opencode/cli scope and the exact build, and say why the frozen @opencode-ai/cli@next line no longer reaches a server this SDK can drive.

Breaking changes

Listed in CHANGELOG.md under [Unreleased]. No published consumer is owed compatibility yet; the release line stays 0.8.0-preview.N.

Verification

• Completion gate on Windows: slopwatch 0 issues, generate --verify, refresh-spec --verify, Release build 0 warnings, both format passes, 5,177 tests, 0 failed, 0 skipped across nine assemblies.
• Distributed-build consumer leg on Windows: @opencode/cli@0.0.0-beta-19425 installed from npm into an isolated prefix and started with isolated XDG roots; the whole OpenCode.Sdk.Tests assembly on net10.0 attached to it passed 1,102 of 1,103 (the one failure is the RPC event proof's own refusal of an external endpoint); the sandbox breadth walkthrough, --paginate, and --standalone (launcher over the npm executable with an explicit Command) all ran against that build.
• Linux and macOS live lanes at the new pin are what this PR's CI run is for.

Not in this PR

The Windows launcher default (["opencode2", "serve"] never resolves the npm .cmd shim), the terminal Submit door, the durable-envelope hoisting rule, and the consumer-documentation corrections follow in their own pull requests.