Sync main 14892075 into the cutover

[SaladDay]

Merges main 1489207 into aos/cutover, through aos/main-sync-5. It brings #517 (the process deployment path deleted), #521 (the Sandbox Provider protocol in one file) and #523 (Agent request shapes generated from the pinned schema).

Resolution:

• main's deletions win: the process deployment, the local node, web_managed, local_node_id, admission_paused, direct-capacity limits and the optional Provider side interfaces.
• aos's design wins where it replaced a mechanism: Bootstrap.SandboxIO and the single Bootstrap.Validate (now in main's sandbox_provider.go), Serve credentials, SandboxLink(), and no PublicOrigin requirement.
• runtime_lifecycle.go, runtime_compute.go, managed_setup.go and session_model_defaults.go keep both intents.
• TestLinkAuthorityDestroyedAllocation moved onto main's Web deployment fixtures.

Migrations: 000093 web_deployment_only (main), 000094 session_runtime_assignments, 000095 sandbox_link_authority.

Checks:

• build, vet, darwin/windows daemon builds;
• sqlc, make openapi, the Harness catalog, the specification contract and the E2B contract generator, all with no diff;
• focused tests (execution, deployment, sandbox including the node package, api, sessions, cmd, runtimegateway, runtimeobs, sandboxlink, v1), deploymentpg and sessionpg on a fresh database;
• the Core integration suite, make check-e2b-provider, make check-names check-docs check-ci.

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