Dead run(host) parameter on all 20 seam entry points

Codex multi-host support (ADR-0011). Code under review is on branch feat/codex-support-m0, not main. ca-codex ships BETA; these are blocking-severity for the affected code but nothing is merged to the default branch yet.

Severity: med | Confidence: 0.85 | Group: dead-run-host-param

Where:

• core/pysrc/pre-write.py:153-164
• core/pysrc/pre-edit.py:205-216
• core/pysrc/_hooklib.py:76-84
• core/pysrc/session-start.py:541-556
• core/pysrc/pre-bash.py:875-886
• core/pysrc/post-write-edit.py:185-196
• core/pysrc/security-pass.py:94-105
• core/pysrc/migration-pass.py:100-115
• core/pysrc/taskwrite.py:125-133
• core/pysrc/pre-read.py:62-73
• core/pysrc/session-start.py:690-701
• core/pysrc/git-enforce.py:293-304
• core/pysrc/hostapi.py:176-192

Evidence / impact:

• (architecture-001) Every one of the 20 entry scripts defines def run(host, argv=None) per ADR-0011's 'importable run(host) functions' shape, but a mechanical scan of all 20 run() bodies shows NONE references host — each delegates to main(), which re-acquires the host through the hidden module-global _hooklib.get_host() / a fresh hostapi.load_host() (e.g. session-start.py:541 calls hostapi.load_host() insid
• (architecture-001 impact) The parameter promises dependency injection it does not deliver: run(fake_host) silently runs against the disk-loaded _host.py instead, so contract tests exercising 'same entry, two hosts' through run() would be testing the wrong host without failing. It also masks that the real seam wiring is a g
• (performance-002) Every entry script's main guard does sys.exit(run(hostapi.load_host()) or 0) — an eager, explicit call to hostapi.load_host(), which does importlib.util.spec_from_file_location + module_from_spec + spec.loader.exec_module(mod) on _host.py beside it (hostapi.py:183-189). That loaded host is then passed into run(host, argv=None), but every run() in the audited scripts (pre-writ
• (performance-002 impact) Every single hook invocation across the whole hook surface (both the ca and ca-codex plugins, ~19 entry scripts) pays the file-load + exec_module cost of _host.py twice instead of once. Per-call cost is modest (a small already-cached file, tens to a couple hundred lines of Python to parse/exec), s

Recommendation:

Remove the host parameter from run(host, argv=None) on all 20 entries, or wire it so run(host) truly injects. Today every run() ignores it and re-acquires the host via the module global, so _host.py is exec-loaded twice per invocation (performance-002).

Acceptance criteria:

• run(host) either injects the passed host or the parameter is gone.
• _host.py is loaded at most once per hook process.

Folds (same root cause / corroborating findings): architecture-001, performance-002