feat: Journey Matcher — the delta explains the journey (Delta -> Journey, ADR-011)

The sanctioned last architectural building block. Reverses the order: not Goal -> Journey -> Delta
but Goal -> Required -> Delta -> Journey. A Journey is the EXPLANATION of the Capability Delta, not
its cause — so this is a Matcher/Explainer, not a Selector.

New module compliance/journey_matcher/ = the third independent, interchangeable function of the
pipeline, beside Company 2A (Evidence -> Capability) and RS-005 (Capability -> Delta):

  match_journeys(delta, journeys, context) -> ranked, auditable explanation

- Looks ONLY at the Capability Delta — never at certificates, regulation, tenders or the goal.
  Journey signatures are certificate-agnostic capability clusters (Input -> Output pattern).
- score = share of the delta a journey explains (recall over the missing capabilities); journey_only
  documents where a journey reaches beyond the delta so a broad journey is not silently preferred.
- Deliberately dumb + deterministic (pure set overlap; NO ML/embeddings/LLM), fully auditable
  (matched / unexplained / journey_only / context signals); a learning ranker can sit on top later.
- Signatures injected, engine hermetic. mypy --strict clean.

Validated on the real patterns (demo): a CRA+MaschinenVO delta ranks the convergence journey 100%,
"ISO27001 -> CRA" 56% (misses the machine-safety caps), "ISMS -> TISAX" 0%. This resolves the
"Scope -> Journey" jump from Customer Mission #1. Freeze exception explicitly authorised; non-runtime
-> no deploy. 12 tests pass, check-loc 0.

backend-compliance/compliance/journey_matcher/schemas.py

@@ -0,0 +1,66 @@
+"""Schemas for the Journey Matcher — the Delta -> Journey function of the Capability Delta Engine.
+
+Derived views (computed-not-stored): nothing here is persisted; every match is recomputed from the
+input delta + injected journey signatures each call. No new corpus, no graph (freeze v1.0).
+Python 3.9 compatible (no `|` unions).
+"""
+
+from __future__ import annotations
+
+from typing import List, Optional
+
+from pydantic import BaseModel, Field
+
+
+class JourneySignature(BaseModel):
+    """A known journey described ONLY by its capability pattern (Input cluster -> Output cluster).
+
+    Deliberately certificate-/regulation-agnostic: the match uses `capability_pattern` alone. `label`
+    and the context fields exist for the human-auditable explanation, NEVER for the score. (Today the
+    signatures are derived from the transition patterns; the IDs like "ISO27001->CRA" are just one way
+    to describe the clusters — the matcher never reads them.)
+    """
+
+    journey_id: str
+    label: str
+    capability_pattern: List[str] = Field(default_factory=list)     # OUTPUT cluster: the delta this journey is about
+    assumed_capabilities: List[str] = Field(default_factory=list)   # INPUT cluster: typically already present
+    industry: Optional[str] = None
+    product_type: Optional[str] = None
+    target_type: Optional[str] = None        # context only: regulation / certification / contract / environmental
+
+
+class MatchContext(BaseModel):
+    """Optional corroborating context — surfaced as documented reasons, never part of the score."""
+
+    industry: Optional[str] = None
+    product_type: Optional[str] = None
+    target_type: Optional[str] = None
+
+
+class JourneyMatchReason(BaseModel):
+    """The auditable WHY behind one match — everything a reviewer needs, no opaque score."""
+
+    matched_capabilities: List[str] = Field(default_factory=list)   # delta INTERSECT pattern (what it explains)
+    unexplained_delta: List[str] = Field(default_factory=list)      # delta - pattern (what it does NOT explain)
+    journey_only: List[str] = Field(default_factory=list)           # pattern - delta (journey covers, not needed here)
+    context_signals: List[str] = Field(default_factory=list)        # "gleiche Zielart", "gleiche Branche", ...
+
+
+class JourneyMatch(BaseModel):
+    """One known journey, ranked by how much of the delta it EXPLAINS (not how well it 'fits')."""
+
+    journey_id: str
+    label: str
+    score: float = 0.0                       # |delta INTERSECT pattern| / |delta|, 0..1: share of the delta explained
+    explains: str = ""                       # "8 von 10 fehlenden Capabilities"
+    reason: JourneyMatchReason
+
+
+class JourneyMatchResult(BaseModel):
+    """Ranked known journeys that EXPLAIN a Capability Delta. Journey = explanation, not cause."""
+
+    delta_size: int = 0
+    matches: List[JourneyMatch] = Field(default_factory=list)       # ranked desc by score
+    best: Optional[JourneyMatch] = None
+    headline: str = ""