Add Orchestrator collaboration mode

[richardgetz]

Summary

• add Orchestrator to the TUI-visible collaboration modes and collaboration-mode presets/templates
• rename user-facing router thread-control config/API/schema/docs to orchestrator with no router compatibility alias
• add Orchestrator-scoped memory behavior so scoped threads only become memory-eligible while Orchestrator mode is active
• add spawn_agent.collaboration_mode so Orchestrator can launch child agents in default, plan, continuous, or orchestrator mode
• initialize selected child collaboration modes at thread spawn time, including fork inheritance from live parent state or persisted rollout turn context
• document the intended Orchestrator parent/child model plus next steps for task graph APIs, callbacks, trusted wake channels, and Orchestrator-scoped memory writes

Breaking Change

• [thread_control.router] and public router thread-control mode names are replaced by [thread_control.orchestrator] / orchestrator.

Tests

• just write-config-schema
• just write-app-server-schema
• cargo check -p codex-core -p codex-app-server-protocol -p codex-app-server -p codex-tui -p codex-models-manager -p codex-config -p codex-protocol
• cargo test -p codex-core thread_control
• cargo test -p codex-core config::schema::tests::config_schema_matches_fixture
• cargo test -p codex-tui collab
• cargo test -p codex-core orchestrator_memory_scope_only_enables_during_orchestrator_mode
• cargo test -p codex-rollout
• cargo test -p codex-app-server thread_list
• cargo test -p codex-core multi_agent_v2_spawn -- --test-threads=1
• cargo test -p codex-core requested_spawn_agent_collaboration_mode -- --test-threads=1
• cargo test -p codex-core spawn_agent_description -- --test-threads=1
• cargo test -p codex-tools agent_tool -- --test-threads=1
• just fmt
• just fix -p codex-core -p codex-tools -p codex-models-manager
• git diff --check
• just fix -p codex-protocol -p codex-config -p codex-core -p codex-rollout -p codex-thread-store -p codex-app-server-protocol -p codex-app-server -p codex-tui -p codex-models-manager -p codex-analytics -p codex-collaboration-mode-templates

Review

• Ran $post-change-review with independent reviewers across the Orchestrator mode/config/memory changes and the child collaboration-mode follow-up.
• Fixed review findings around preset model masking, child session initialization order, full-history fork inheritance, unloaded-parent rollout fallback, and preserving fork caller model overrides.

Notes

• A broader workspace test run hit local sandbox sandbox-exec: sandbox_apply: Operation not permitted failures in command_exec/js_repl-related tests; the focused affected tests above passed.