refactor(harnesses/claude): collapse 8 subdirs into 3 deep internal modules

[lespaceman]

Files

• src/harnesses/claude/{auth,config,hooks,process,protocol,runtime,session,system}/ — 8 sibling subdirs
• src/harnesses/claude/adapter.ts (~99 LOC) — orchestrator
• src/harnesses/contracts/ — shared HarnessAdapter interface (Claude/Codex/Mock)

Problem

Eight peer subdirectories imply eight architectural seams; in practice, only adapter.ts consumes them, in a fixed wiring, with no swappable adapters at any of those seams. Most subdirs export 1–2 things and have a single call site. The flat shape advertises modularity that doesn't exist (one adapter = hypothetical seam).

Sketch of deepening

Three deep internal modules behind the existing HarnessAdapter external interface:

1. Protocol Translator — Claude hook payloads ↔ RuntimeEvent/RuntimeDecision. Absorbs protocol/, hooks/.
2. Process Manager — subprocess lifecycle, signals, stdio, system probes. Absorbs process/, system/.
3. Session Controller — auth, config, permissions, session state, runtime state. Absorbs auth/, config/, session/, runtime/.

HarnessAdapter interface (shared across Claude/Codex/Mock) is unchanged.

Why this deepens

• Locality: "where does Claude hook translation live?" → one module instead of two subdirs.
• Real seams emerge: a test could swap Protocol Translator while keeping the real Process Manager, instead of rebuilding the whole MockAdapter. Two adapters becomes a real seam.

Open design questions

• Is the proposed 3-way split actually the right cut? Maybe 2 (lifecycle + translation) or 4 (separating auth from session).
• Does anything in system/ (e.g. environment probing) belong in Process Manager or Session Controller?
• How does this affect the Codex harness? Codex has fewer subdirs but mirrors the structure — should it follow the same 3-module shape for symmetry?

Effort

High — structural reorganization across ~8 subdirs. Affects imports across the harness layer.

Risk

Highest of the five. Worth doing only if locality friction is real (not aesthetic). Grill before committing.