fix(server): own provider generation lifecycle through shutdown

[timigod]

Outcome

Makes provider generations, snapshots, managed loads, session startup, and provider-owned processes retain truthful ownership through refresh, timeout, replacement, abort, and daemon shutdown.

Changes

• drain refresh and load operations before unregistering ownership
• bound provider-load draining before terminal client shutdown
• make cleanup run on both fulfillment and rejection
• prevent registration after shutdown begins
• cancel acquisition and replacement work at the owning boundary
• close superseded clients and preserve managed-process truth
• add protocol-compatible provider lifecycle receipts and regressions

Startup cancellation amendment

• propagate shutdown cancellation through direct and wrapped create, resume, and reload startup
• make ACP initialization abortable and bound courtesy close while terminating child processes concurrently
• dispose Codex children that resolve after startup cancellation and own late cleanup rejection
• retain OpenCode acquisition after session creation begins, delete late-created sessions, own cleanup failures, and drain cleanup before shutdown
• pass OpenCode acquisition cancellation to the server manager so canceled callers do not retire reusable shared generations

OpenCode teardown amendment

• forward startup cancellation into the native session.create request
• terminally bound failed-create cleanup so shutdown releases the helper runtime when the SDK ignores cancellation
• start native close abort without waiting behind event-stream teardown and bound both non-cooperative operations
• fence native abort and ephemeral deletion by server-scoped session generation so a superseded reload cannot abort its replacement

Final lifecycle amendment

• register create and resume startup ownership before asynchronous acquisition begins
• cancel active startup during client shutdown and drain its terminally bounded cleanup before server-manager shutdown
• make startup provider.list signal-aware and bounded while retaining the raw SDK operation until actual settlement
• bound ephemeral session.delete before releasing the server while retaining the raw delete operation
• use completion order for same-session generations and concurrent manager reload swaps
• serialize reload swaps with explicit close so each displaced replacement is closed and cannot be orphaned

Current-main integration

• merged official main at 70ed70d36e2eabd3876a22931954319ec202c902 with an ordinary two-parent merge
• resolved the sole textual conflict by retaining both the provider ownership regressions and current-main base-environment coverage
• preserved current-main OpenCode busy-status and turn-cancellation behavior

PR #2744 integration guidance

Do not combine this branch with draft PR #2744. During later integration, normalize all OpenCode acquisition methods to one options-object shape:

• acquireCurrent(options?: { signal?: AbortSignal })
• acquireNew(options?: { signal?: AbortSignal })
• acquireDedicated(env, options?: { signal?: AbortSignal })

Translate this branch's positional startup calls to { signal }, including dedicated acquisition, while retaining #2744's waiter-aware cancellation and shutdown implementation.

Verification

• OpenCode provider file: 102 tests passed
• Agent manager file: 147 tests passed
• prior branch-wide focused provider lifecycle matrix: 644 tests passed with 1 existing platform-dependent skip
• npm run build:server
• npm run typecheck
• npm run lint: 0 warnings and 0 errors
• npm run format:check
• git diff --check
• official-main-relative whitespace and patches/ checks
• commit hooks reran formatting, lint, and all-workspace typecheck successfully

Exact receipt

• Official current-main base: 70ed70d36e2eabd3876a22931954319ec202c902
• Repair head before integration: 0facad3e0535991a32e72055b5e0ab9e861b02c6
• Integration merge: 833a60dabb8d1681b7478defe5b5abf86abc00f0
• Startup amendment: 584471d82b0aec902cf0d249b4e26479ce0ac7a5
• Cancellation ownership amendment: 0d8fbd9b2cff87a2bf980a4c49589747dff24016
• OpenCode teardown amendment: 76d72382253ad17e43eaec6811893e91dac881c5
• Final lifecycle amendment / PR head: 653b8b9c0f4bd19fdf10bd6aaeb2782cca5008d8
• Amendment parent: 76d72382253ad17e43eaec6811893e91dac881c5
• Exact tree: 0ea257185b384ece2dd65a814a7ef3d1df420a28

This PR remains draft pending exact-tip rereview.

[timigod]

Closed as superseded by focused successor #2758 at independently accepted head 2adf9c7587a1e78606e0c2e4b680794c26da0bc0. The successor reconstructs the unique provider-generation ownership and provider-health/status behavior on current upstream, adds the shared monotonic shutdown deadline and bounded concurrent drain, and preserves mixed-version compatibility. This branch and discussion remain available as historical evidence; no branch is deleted.