Audit caller-aware access and free-tier signal shapes

[YE-YI7]

What changed

• adds a deterministic audit over the 30 committed library manifests
• records the audit result and decision-ready interpretation
• adds a vendor-scoped candidate access extension for ai-catalog#83
• models non-authoritative prices as priceEchoes[]
• models compound allowances as freeTierRules[]
• reserves an authenticated pricingResolver reference for caller-specific terms
• validates all 30 candidate objects against a JSON Schema

Why

New feedback in Agent-Card/ai-catalog#83 identified two weaknesses in a scalar discovery price: negotiated caller-specific prices and compound free-tier limits. The audit measures those gaps against ASM's real library before proposing a WG-neutral namespace.

Headline findings:

• 22/30 manifests advertise a free tier
• only 8/22 have any allowance description
• 0/22 have machine-readable free-tier rule sets
• Perplexity already loses one of two positive price dimensions in the legacy cheapest-scalar projection
• ATTOM has a concrete coarse-tier conflict: it derives as free while the manifest says production access is sales-led after a 30-day trial
• six resolver candidates are a text-review queue, not six verified personalized contracts

This PR does not change ASM v0.3 or the live catalog projection. It keeps the candidate under an ASM-owned namespace until the WG chooses a neutral extension key.

Validation

• python experiments/access_signal_shape_audit.py --pretty
• independent jq recomputation of the headline counts
• python -m pytest scorer/test_ai_catalog_access_extension.py -q — 3 passed
• python -m pytest scorer -q — full Python suite passed
• python -m compileall -q asm_access_extension.py experiments/access_signal_shape_audit.py
• git diff --check