perf(context)!: make filesystem LLM scoring opt-in

[LukasParke]

What

• default filesystem() relevance scoring to the local path heuristic
• call an LLM only when scoringModel is explicitly configured
• normalize blank model strings to the heuristic path
• use a shorter append timeout when no model scoring is configured

Why

The previous default silently issued a Haiku request for each new #file reference inside the append pipeline. File relevance scoring should not create hidden model cost and latency. The deterministic path heuristic is sufficient as the safe default; applications that need semantic scoring can opt in.

This semantically ports the filesystem portion of fork/port/openrouter-fixes commit fb22ac35 onto current filesystem() names.

Test plan

• 28 focused filesystem tests pass
• context/core typechecks
• root lint
• sentrux check .
• source worker package/context tests and structural gate pass
• clean-context Pi review; blank-string opt-in fixed

Breaking change

scoringModel no longer defaults to Haiku. Callers relying on semantic relevance must configure a model explicitly. The default now performs no model call.

[vercel]

@LukasParke is attempting to deploy a commit to the Matt Apperson's projects Team on Vercel.

A member of the Team first needs to authorize it.

[LukasParke]

Agent: The code CI, DCO, and structural gate passed. Remaining red checks are external configuration: compat received an empty OPENROUTER_API_KEY, and Vercel requires upstream deployment authorization. I cannot remediate or rerun those checks without upstream repository access/secrets.