Remove this unused API. This API is insidious in that it implies that
alive state should be determinable from the caller, and implies that a
preflight should indicate routing. Lets drop this, and handle errors
correctly from a failed session in the future.
## Summary
- Retain the first pre-observation `yield_control()` boundary when a
cell completes before observation.
- Deliver the preserved yield before the buffered completion.
- Keep later unattached yields as no-ops.
## Why
Create followed by the initial wait must preserve the former execute
response boundary even when the script runs to completion first.
## Impact
The first wait observes the same initial yield boundary as before create
and observe were decoupled.
## Validation
- Focused initial-yield signature regression passed.
- Stack-tip validation: `just test -p codex-code-mode -p
codex-code-mode-protocol` (70 passed).
- Parent branch:
`cconger/code-mode-runtime-compact-03e2-observation-delivery`.
## Summary
- Give each session and cell a hierarchical cancellation token.
- Track cell tasks so shutdown waits for admitted actors without polling
the registry.
- Make shutdown authoritative across concurrent admission and
non-cooperative callbacks.
## Why
A best-effort registry scan can miss cells admitted concurrently or
blocked behind the registry lock.
## Impact
Session shutdown reliably stops every admitted cell and rejects new work
once shutdown begins.
## Validation
- Stack-tip validation: `just test -p codex-code-mode -p
codex-code-mode-protocol` (70 passed).
- Parent branch: `cconger/code-mode-runtime-compact-03c-terminal-state`.
## Summary
- Introduce a single cell terminal-state machine for completion and
termination.
- Make stored-value commits atomic with the winning terminal outcome.
- Buffer terminal results for later observation and cover
termination-before-commit behavior.
## Why
Completion, termination, observation, and stored-value updates must
agree on one linearized outcome under cancellation races.
## Impact
Terminal delivery becomes deterministic and terminated cells cannot
commit state after termination wins.
## Validation
- Focused terminal-state regression passed.
- Stack-tip validation: `just test -p codex-code-mode -p
codex-code-mode-protocol` (70 passed).
- Parent branch:
`cconger/code-mode-runtime-compact-03b-session-runtime`.
## Summary
- Move code-mode cell ownership and shared stored values from
`CodeModeService` into `SessionRuntime`.
- Keep the protocol-facing execute/wait behavior behind the existing
service adapter.
- Add runtime-level ownership and isolation coverage.
## Why
This establishes a transport-neutral session boundary before later
lifecycle and create/observe changes.
## Impact
No intended model-facing behavior change. This is an ownership and
layering refactor.
## Validation
- Stack-tip validation: `just test -p codex-code-mode -p
codex-code-mode-protocol` (70 passed).
- Parent branch: `cconger/code-mode-runtime-compact-03a-runtime-types`.
## Summary
- introduce a private `session_runtime` boundary for cell creation
requests, observation modes, lifecycle events, output items, and tool
metadata
- update the cell actor and in-process service to use those
transport-neutral types
- keep cell ID allocation on the owning session side
## Motivation
Cell lifecycle vocabulary currently lives inside the cell actor
implementation. That makes the service adapter and future session
runtime depend on actor-specific types, increasing the size and
complexity of the runtime ownership change.
This is the first reviewable slice of the session-runtime stack. It
separates the transport-neutral data model without moving lifecycle
ownership or changing behavior.
Later slices will move session state behind this boundary, harden
terminal and shutdown behavior, and split cell creation from
observation.
## Behavior
There are no public API or user-visible behavior changes in this PR.
In particular:
- `CodeModeSession::execute` and `wait` are unchanged
- cell IDs remain allocated by the owning session
- cell admission, observation, termination, and shutdown behavior are
unchanged
