feat(ST-707): log tools — implementation, test_result, commit

Three write tools that append StoryLog entries:
- log_implementation: type=IMPLEMENTATION_PLAN
- log_test_result: type=TEST_RESULT, status PASSED|FAILED
- log_commit: type=COMMIT with hash and message

All accept optional metadata in input but skip writing it for now —
the StoryLog.metadata JSONB column lands with Scrum4Me PR #2.
After that PR merges, run sync-schema and add `metadata` to each
prisma.create's data field.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/tools/log-implementation.ts

@@ -0,0 +1,43 @@
+import { z } from 'zod'
+import type { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js'
+import { prisma } from '../prisma.js'
+import { requireWriteAccess } from '../auth.js'
+import { userCanAccessStory } from '../access.js'
+import { toolError, toolJson, withToolErrors } from '../errors.js'
+
+// metadata is accepted on input but not yet written — schema sync after
+// Scrum4Me PR #2 lands adds the StoryLog.metadata JSONB column.
+const inputSchema = z.object({
+  story_id: z.string().min(1),
+  content: z.string().min(1),
+  metadata: z.record(z.string(), z.unknown()).optional(),
+})
+
+export function registerLogImplementationTool(server: McpServer) {
+  server.registerTool(
+    'log_implementation',
+    {
+      title: 'Log implementation plan',
+      description:
+        'Append an IMPLEMENTATION_PLAN entry to a story log. ' +
+        'Forbidden for demo accounts.',
+      inputSchema,
+    },
+    async ({ story_id, content }) =>
+      withToolErrors(async () => {
+        const auth = await requireWriteAccess()
+        if (!(await userCanAccessStory(story_id, auth.userId))) {
+          return toolError(`Story ${story_id} not found or not accessible`)
+        }
+        const log = await prisma.storyLog.create({
+          data: {
+            story_id,
+            type: 'IMPLEMENTATION_PLAN',
+            content,
+          },
+          select: { id: true, created_at: true },
+        })
+        return toolJson({ id: log.id, created_at: log.created_at })
+      }),
+  )
+}