feat: upgrade fast-agent-mcp to 0.7.22, add Fable 5 / Opus 4.8 Mantle wire names

Bumps the runtime from 0.7.15 to 0.7.22 (last 0.7.x release). All five
monkey-patched surfaces (MCPAgentClientSession.send_request/call_tool,
MCPAggregator._execute_on_server/_create_session_factory/call_tool),
ToolRunnerHooks, and both AnthropicConverter private methods patched by
mantle_shims were verified unchanged in signature at 0.7.22.

Adds claude-opus-4-8 and claude-fable-5 to MANTLE_WIRE_NAMES; both are
natively known to fast-agent's ModelDatabase as of 0.7.17+ (1M context).

58/58 tests pass; server/patch modules import cleanly on 0.7.22.

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

pallas/mantle_shims.py

@@ -42,6 +42,8 @@ logger = logging.getLogger(__name__)
 MANTLE_WIRE_NAMES: dict[str, str] = {
     "claude-haiku-4-5": "anthropic.claude-haiku-4-5",
     "claude-opus-4-7":  "anthropic.claude-opus-4-7",
+    "claude-opus-4-8":  "anthropic.claude-opus-4-8",
+    "claude-fable-5":   "anthropic.claude-fable-5",
 }