refactor: Phase 3 — split workspace.ts and plugin.ts by responsibility

[vriesd]

Summary

Phase 3 of the runtime refactor plan (.agents/plans/13-runtime-refactor/README.md). Stacked on #90; retarget once that merges.

Two file splits plus one follow-up from the final review:

• infrastructure/fs/workspace.ts split into workspace-paths.ts (root validation and .flow layout), managed-fs.ts (managed filesystem primitives), session-lock.ts (cross-process lock), and a 299-line workspace.ts keeping only the session file protocol. Every function body moved verbatim; every importer repointed, including two the plan's file list missed (source-identity.ts and the persistence test's child-process import URL). workspace.ts re-exports nothing except ArchiveCollisionError. The new files form a strict DAG with no backward edges.
• platform/opencode/plugin.ts split into command-hook.ts, tool-guard.ts, and a wiring-only plugin.ts. Three deliberate changes, all named in the plan: the plugin resolves its workspace through resolveWorkspaceRoot at load (validation moves from the first tool call to plugin load; no valid workspace is affected, and the leadership registry key is unchanged because it already realpathed); one FlowService per plugin instance for the command hook and auto-drive status reads instead of one per call (the whole factory chain is stateless, so this is equivalent); the two session.deleted checks in the event hook merged into one branch. The per-call resolution inside tools.ts is deliberately kept: tools must resolve from their own ToolContext.
• Follow-up commit: the load-time refusal is now logged through the host before rethrowing, with a test that loads the plugin from the home directory and asserts both the rejection and the log line. docs/development.md names the new modules; the docs byte cap forced a prose trim in the same file.

No prompt text, guidance, Zod schema, tool name, tool response field, Session v5 shape, or error message changes.

Test plan

• bun run check at ab97a60: 1231 pass, 1 skip, 0 fail
• bun run smoke:live against a reachable OpenCode host: 22 pass. Note: the smoke used a valid workspace, so it does not exercise the new load-time refusal path; the unit test above does.
• Task-scoped review of each commit, both diffed block by block against the pre-split files, approved
• Whole-branch review: ready with fixes; the one Important finding (unlogged load-time throw) is fixed and re-reviewed

Deferred follow-ups (not blocking)

• The docs byte trim softened three qualifiers in docs/development.md ("must" in Documentation, "immediately" in Release, "intentionally" in Change discipline). Phase 4 edits the same section and restores them.
• workspace-validation.ts carries its own lstat/open/realpath primitives that overlap managed-fs.ts; consolidating is a natural later step.
• guardTools keeps positional parameters while createCommandHook takes an options object; justified by what each needs, revisit only if a parameter is added.

🤖 Generated with Claude Code

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-18T07:26:21.317372Z	ab97a60	PR opened

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