docs(#2584): ADR-1239 Codex-binding amendment + dispatch.isolation capability (Phase 0) (#2600)

* docs(#2584): add ADR-1239 Codex-binding amendment + dispatch.isolation capability

* chore(#2584): backfill changeset PR number (#2600)

docs/reference/host-integration-capability-matrix.md

@@ -100,6 +100,7 @@ Sources consulted:
 | dispatch.background | true | https://github.com/openai/codex/blob/main/codex-rs/core/src/tools/handlers/multi_agents_spec.rs | "spawn_agent returns the spawned agent id immediately; a separate wait_agent tool polls for final status." |
 | dispatch.subagentToolkit | full | https://developers.openai.com/codex/multi-agent | "Subagents inherit the sandbox policy and tool surface from the parent session." |
 | dispatch.backgroundDispatch | true | https://github.com/openai/codex/blob/main/codex-rs/core/templates/collab/experimental_prompt.md | "Sub-agents have access to the same set of tools as you do so you must tell them if they are allowed to spawn sub-agents themselves or not." The config (codex-rs/config/src/config_toml.rs) exposes an |
+| dispatch.isolation | orchestrator-worktree | https://learn.chatgpt.com/docs/environments/git-worktrees ; https://github.com/openai/codex/blob/main/codex-rs/utils/cli/src/shared_options.rs | "Worktrees are available only in Codex in the ChatGPT desktop app." (no native CLI worktree) + `codex exec --cd <dir>` sets an explicit working root, so GSD creates+manages the worktree and points the executor at it (#2584) |
 
 **GSD integration status — Phase D dogfood complete (#2088, ADR-1239).** Codex installs through the `declarative` embedding adapter (`createDeclarativeAdapter` → `installRuntimeArtifacts`); the hardcoded `runtime === 'codex'`/`isCodex` projection is folded into descriptor-driven `runtime.hostBehaviors`, and install/uninstall output is byte-parity-gated (`tests/fixtures/golden-install-parity/codex.json`). Three capability upgrades land, each with a test driving the user-reachable surface: