[SaladDay]

Function calls and results move out of store into sessions and sessionpg. This PR also introduces the lease-bound Session execution skeleton.

What changes

• Execution skeleton:
  • sessions.ExecutionOperations with ExecutionStorage { FunctionExecution }.
  • sessionpg.Execution{lease}.
  • execution.Owner.Sessions.
  • Dispatcher.Bind(owner): StartWorker binds through it, and a Dispatcher that runs Turns outside a Worker binds the same way. The Session execution operations are unexported on the Dispatcher.
• Function execution:
  • RecordFunctionCall, PendingFunctionCalls and ConfirmFunctionResult run on the lease under the Session lock.
  • Each one loads facts, decides with pure sessions rules, then applies. The Turn status change and its journal entries are settled in the same order as before.
• Result admission: sessions.AdmitFunctionResult is a procedure over a four-method Tx that sessionpg.BindSession implements. It runs inside the public SubmitInputs transaction.
• Required actions: LoadRequiredActions is the lock-free snapshot read used by scheduling.
• Removed from store:
  • function_calls.go, function_inputs.go, function_results.go and function_state.go;
  • the test-only GetFunctionCall/SubmitFunctionResult. Tests now submit results through the public tool_result input.
• Tests:
  • The store test harness binds one execution lease per harness. Restart tests observe the lease release before they reacquire it.
• Docs: IMPLEMENTATION.md and sessions/doc.go name the new owners.

Behavior

Unchanged. The api mapping and precedence are the same for ErrFunctionCallTurnMismatch, ErrUnknownFunctionCall and ErrFunctionResultConflict, and so are idempotent replay, the pending order and the conflict rules.

Checks

• go build ./... and go vet ./services/core/....
• sessions and sessionpg in full. The PostgreSQL tests cover rollback, a concurrent single winner, scoping, a closed lease and the ownership handoff.
• execution -run '^(TestStartWorker|TestWorkerRun|TestFunction|TestSandboxReset|TestSandboxDeploymentDrain|TestCommittedResetView|TestFinishRun)'.
• cmd/server, and the api function and tool_result tests.
• Store: an exact-name sweep over 182 tests. It covers every test that builds or uses a Dispatcher, dispatch harness, worker or execution owner, and it ran with the pinned official SDK. The 11 skips are native-daemon cases.
• scripts/check-names.py and make check-docs.

A blind review found one blocker (an unbound Dispatcher in a store test) and three minor issues. All are fixed in this commit.

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