fix(entitlements): gate paid MCP tools (send_invoice/agi_submit/vat_declaration_submit) server-side (#846)

The HTTP routes call requireCapability at every paid chokepoint, but the
MCP/agent path bypassed the paywall entirely: the three external-service
tools stage operations whose commit calls the email / Skatteverket services
directly, with no capability check. After the 2026-07-07 trial cutover a
trial-connected non-payer using the gnubok MCP connector could still send
invoice emails and file AGI/VAT.

Close the gap with two layers, mirroring the existing TOOL_SCOPE_MAP gate:

- Dispatch gate (mcp-server/server.ts): MCP_TOOL_CAPABILITY_MAP, checked
  right after the scope check, blocks a non-entitled company before any
  pending op is staged. Emits errorKind='capability_denied' telemetry.
- Commit-time gate (commitPendingOperation): PAID_OPERATION_CAPABILITY_MAP,
  checked before the atomic claim. The real external-service chokepoint —
  applies to the MCP approve tool AND the UI approval path, and closes the
  trial-connected-token window (the grant has expired by commit time). A
  blocked op stays 'pending', so it is re-approvable once the company subscribes.

Adds a transport-free capabilityBlockedError() helper (shared bilingual
copy) and locks both maps with tests (maps, dispatch gate, commit gate).
Only the three write/submit tools are gated; SKV read/local tools stay free
per the statutory carve-out. No DB/migration change; self-hosted stays all-on.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/events/types.ts

@@ -168,7 +168,7 @@ export type CoreEvent =
       success: boolean                              // true iff the tool returned without throwing AND was invoked (not denied)
       isError: boolean                              // matches the JSON-RPC tool-result isError flag returned to the client
       errorCode: string | null                      // structured error code from tool-result.toToolError when applicable
-      errorKind: 'execution' | 'scope_denied' | 'unknown_tool' | null
+      errorKind: 'execution' | 'scope_denied' | 'capability_denied' | 'unknown_tool' | null
       errorMessage: string | null                   // human-readable error message (truncated to 500 chars), null on success.
                                                     // Raw material for clustering real agent failures into curated gotchas —
                                                     // errorCode alone can't distinguish "period locked" from "unbalanced".