Implement WP-0015-T03: Control Plane reference-rendering routes

New service/reference_docs.py renders specs/policies/*.md and
specs/profiles/*.md read-only at request time via a small markdown
library (added markdown + PyYAML to the service extras) -- not a
static-build pipeline, matching the WP-0012-T03 decision to skip
state-hub's heavier Observable Framework pattern.

One parameterized route, GET /reference/{kind}/{slug}, covers both
addendum URL shapes. Discovered phase_detail.html's Status table never
displayed the degeneration_policy id at all -- added that row (with
the reference link) rather than wiring a link with nothing to attach
it to. phase_new.html gets a plain link next to the field.

Deliberately did not wire extension-id links into the UI in this task
-- extension ids don't appear anywhere in the Control Plane today
(that's WP-0014's gap, not this one's to expand).

6 new Docker-gated tests. Full suite: 94 passing offline, 164 passing
with Docker (up from 158).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/target_revenue/service/reference_docs.py

@@ -0,0 +1,58 @@
+"""Read-only rendering of `specs/policies/`/`specs/profiles/` markdown
+files for the Control Plane (WP-0015-T03).
+
+Server-side markdown -> HTML at request time, deliberately not a static
+build pipeline (unlike state-hub's Observable Framework Reference
+section, confirmed materially heavier during WP-0012-T03) -- this repo's
+existing lightweight FastAPI+Jinja2 stack needs nothing more than a
+small markdown library for six profile pages and one policy page.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+from typing import Any
+
+import markdown
+import yaml
+
+_SPECS_DIR = Path(__file__).resolve().parents[3] / "specs"
+
+# kind -> subdirectory name under specs/. Only these two exist today
+# (WP-0015-T02); a third kind (e.g. "calculators") can be added here if
+# a future workplan gives calculators their own reference route.
+REFERENCE_KINDS = frozenset({"policies", "profiles"})
+
+
+def load_reference_doc(kind: str, slug: str) -> tuple[str, dict[str, Any]] | None:
+    """Return (rendered_html, frontmatter) for one spec file, or None if
+    `kind` is unknown or no matching file exists. Read-only: there is no
+    corresponding write path anywhere in this module."""
+    if kind not in REFERENCE_KINDS:
+        return None
+    path = _SPECS_DIR / kind / f"{slug}.md"
+    if not path.is_file():
+        return None
+
+    raw = path.read_text(encoding="utf-8")
+    frontmatter: dict[str, Any] = {}
+    if raw.startswith("---\n"):
+        end = raw.find("\n---\n", 4)
+        if end != -1:
+            frontmatter = yaml.safe_load(raw[4:end]) or {}
+            raw = raw[end + 5 :]
+
+    html = markdown.markdown(raw)
+    return html, frontmatter
+
+
+def policy_slug_from_id(policy_id: str) -> str:
+    """`trsl:policy:linear-longstop-v0@1.0` -> `linear-longstop-v0`."""
+    name = policy_id.split(":")[-1]
+    return name.split("@")[0]
+
+
+def extension_slug_from_id(extension_id: str) -> str:
+    """`trsl:extension:development-license@1.0` -> `development-license`."""
+    name = extension_id.split(":")[-1]
+    return name.split("@")[0]