fix(hosts): delete five dead HostConfig fields

metadataFormat (generator hardcodes openai.yaml), sidecar (behavior lives in
setup's create_agents_sidecar — knowledge preserved as a comment in codex.ts),
install.prefixable (skill_prefix is implemented entirely in bin/gstack-config),
staticFiles (docstring cited a SOUL.md that never existed anywhere), and
adapter (its only would-be consumer, openclaw-adapter.ts, was fully dead —
with a test asserting the field was undefined). Kept: learningsMode (wired
next), linkingStrategy (validation reads it), coAuthorTrailer (consumed by
resolvers/utility.ts).

Proof: JSON dump diff shows ONLY the deleted keys vanishing; zero-diff regen
across all 10 hosts; host-config + gen-skill-docs suites green. Note: this
commit also carries chunk-23 edits to the shared hosts/claude.ts +
define-host.ts + host-config.test.ts files (skipSkills collapse, stale
line-number comment drops) — pathspec commits, concurrent prep.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CLAUDE.md

@@ -117,7 +117,6 @@ gstack/
 │   ├── gen-skill-docs.ts  # Template → SKILL.md generator (config-driven)
 │   ├── host-config.ts     # HostConfig interface + validator
 │   ├── host-config-export.ts  # Shell bridge for setup script
-│   ├── host-adapters/     # Host-specific adapters (OpenClaw tool mapping)
 │   ├── resolvers/   # Template resolver modules (preamble, design, review, gbrain, etc.)
 │   ├── skill-check.ts     # Health dashboard
 │   ├── test-paid-shards.ts  # Sharded paid-tier runner (one Bun process per shard)