Make market results auditable and preserve missing-data semantics

[bearmug]

Problem

Screening and TA responses are point-in-time values without retrieval provenance, cache state, or explicit partial-result diagnostics. TA currently maps unavailable scores to 0/neutral, and symbol lookup can omit requested symbols without identifying them.

Scope

• Add additive result metadata: retrieval timestamp, source endpoint, cache hit, requested/returned counts, and missing symbols.
• Distinguish unavailable TA data from a genuine neutral signal.
• Validate TA weights and report excluded/unavailable symbols in ranking output.
• Preserve existing top-level result collections for compatibility.
• Add deterministic tests for cache hits, partial symbol results, missing TA values, and invalid weights.

Acceptance criteria

• A caller can tell whether data is fresh, cached, incomplete, or unavailable without reading logs.
• Missing TA values never silently influence a ranking as neutral unless explicitly configured.
• Requested symbols missing upstream are listed in the response.
• Metadata is additive and documented.

Non-goals

No persistence database, scheduler, alert delivery, brokerage integration, or general historical-data platform.