dependency: CAPABILITY_DIMENSION composite trust score (ledger#76)

[mdproctor]

Dependency on casehubio/ledger#76

Tracks the ledger-side implementation of `ScoreType.CAPABILITY_DIMENSION` — per-capability quality dimension scores.

Why devtown needs this

Once implemented, devtown routing policies can specify per-capability quality floors:

```yaml

Today (with CAPABILITY score only):

security-review:
threshold: 0.70 # binary trust floor only

After ledger#76 (with CAPABILITY_DIMENSION):

security-review:
threshold: 0.70
quality:
review-thoroughness: 0.75 # security-specific thoroughness floor
false-positive-rate: 0.20 # security-specific precision ceiling
```

An agent thorough on security (0.92) but careless on architecture (0.31) is routed correctly — the blended global thoroughness score no longer misrepresents their security-review quality.

Impact on Epic 2 design

The current `CapabilityRegistry.threshold()` returns `OptionalDouble` (binary trust floor). Once ledger#76 ships, `RoutingPolicy` can express composite quality requirements. The domain model accommodates this — no rework needed, only additive extension.

Blocking

Does not block Epic 2 — `CapabilityRegistry` and `RoutingPolicy` work with the current ledger and upgrade naturally once ledger#76 ships.

When to apply

After ledger#76 merges and publishes:

1. Add `qualityScore(actorId, capabilityTag, dimension)` call to routing logic
2. Extend `RoutingPolicy` with per-capability dimension floors
3. Update DT-003 in `docs/PROGRESS.md` to reflect richer quality routing

Refs casehubio/ledger#76