feat: mr-reviewer and solution-reviewer join the scaffold, so they exist in a repo

Eleven agents lived only in `~/.claude/agents/`, which is not a git repository —
they would have gone with the laptop. Eight of those were product-specific
reviewers already defined in the projects that need them, and they are removed from
the user level rather than duplicated here. Two were genuinely generic and already
product-neutral (zero references to any product, customer or employer), so they
belong in the shared scaffold: `mr-reviewer` reviews open MRs/PRs on a non-primary
remote in a multi-remote repository, and `solution-reviewer` does a whole-codebase
health review.

`irs-validator` is deliberately NOT brought in. It is personal tooling rather than
a development capability, and per the user CLAUDE.md personal tooling must not be
referenced inside a project repository because those are mirrored to other remotes.

The client manifest gains `fetch` and `websearch` capability mappings, which
`solution-reviewer` needs. Worth noting how that surfaced: the sync REFUSED to
render rather than dropping the two tools silently, which is the fail-safe
behaviour the capability mapping exists to provide — an unmapped capability that
rendered as absent would have quietly removed the agent's web access.

`~/.claude/agents/README.md` now records that ten of the eleven agents there are
installed output from this repository, how to regenerate and reinstall them, and
which one is deliberately personal.

scripts/sync-agent-integrations.py

@@ -205,6 +205,15 @@ def parse_role(source: Path) -> RoleDefinition:
     mutation = metadata["mutation"]
     if mutation not in _MUTATION_POLICIES:
         raise ValueError(f"{source}: unsupported mutation policy {mutation!r}")
+    # A name is an identifier and appears in paths, matrix routing and Rust
+    # constants, so it stays a plain slug. A DESCRIPTION is prose and will
+    # legitimately contain a colon ("problems: missing indexes on FK columns"),
+    # so it is not the author's job to avoid YAML metacharacters — the renderer
+    # quotes it. See `_yaml_scalar`.
+    if ": " in metadata["name"]:
+        raise ValueError(
+            f"{source}: name must be a plain slug, got {metadata['name']!r}"
+        )
     capabilities = tuple(
         item.strip() for item in metadata["capabilities"].split(",") if item.strip()
     )
@@ -237,13 +246,37 @@ def _mapped_capabilities(role: RoleDefinition, client: ClientDefinition) -> list
     return [client.capabilities[name] for name in role.capabilities]
 
 
+def _yaml_scalar(value: str) -> str:
+    """Render a string as YAML that parses back to exactly this string.
+
+    A plain (unquoted) scalar cannot contain `: `, cannot contain ` #`, and cannot
+    begin with an indicator character. HF-2026-001173 shipped a description with
+    `here: ` in it, and the Rust model-policy gate — which parses frontmatter as
+    real YAML — refused the file the sync had just called current.
+
+    Quoting rather than refusing, because a description is prose: MA's
+    `data-architect` reads "…for schema-design and database-health problems:
+    missing indexes on FK/filter/join columns…". Making an author reword that to
+    satisfy a renderer puts the tool's limitation into the standard's wording.
+    """
+    unsafe = (
+        ": " in value
+        or " #" in value
+        or value.rstrip().endswith(":")
+        or value[:1] in "#&*!|>%@`'\"[]{},"
+    )
+    if not unsafe:
+        return value
+    return '"' + value.replace("\\", "\\\\").replace('"', '\\"') + '"'
+
+
 def _render_claude(role: RoleDefinition, client: ClientDefinition) -> str:
     tier = _resolve_tier(role, client)
     tools = _mapped_capabilities(role, client)
     lines = [
         "---",
         f"name: {role.name}",
-        f"description: {role.description}",
+        f"description: {_yaml_scalar(role.description)}",
     ]
     if tier is None:
         # A markdown client declaring tier_policy: unsupported. Not reachable