feat(prd-1): implement M7 - entry point + mode handler integration

- Tag mode routes to fetchForgejoData vs fetchGitHubData based on platform
- createInitialComment auto-detects platform for Forgejo spinner/URL format
- update-comment-link uses updateForgejoCommentBody + Forgejo PR compare URL
- update-with-branch uses platform-aware branch/job-run link formatting
- Agent mode needed NO changes (token in run.ts, rest uses Octokit REST)
- 11 new integration tests in test/m7-integration.test.ts
- 785 tests pass, typecheck clean, format clean

Progress: 78% complete (7/9 milestones) - M3, M8, M9 remaining

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

test/install-mcp-server.test.ts

@@ -352,10 +352,7 @@ describe("prepareMcpConfig", () => {
         repo: "test-repo",
         branch: "test-branch",
         baseBranch: "main",
-        allowedTools: [
-          "mcp__github__create_issue",
-          "mcp__github__create_pr",
-        ],
+        allowedTools: ["mcp__github__create_issue", "mcp__github__create_pr"],
         mode: "tag",
         context: mockContext,
       });
@@ -473,18 +470,16 @@ describe("prepareMcpConfig", () => {
         repo: "test-repo",
         branch: "test-branch",
         baseBranch: "main",
-        allowedTools: [
-          "mcp__github_inline_comment__create_inline_comment",
-        ],
+        allowedTools: ["mcp__github_inline_comment__create_inline_comment"],
         mode: "tag",
         context: mockPRContext,
       });
 
       const parsed = JSON.parse(result);
       expect(parsed.mcpServers.github_inline_comment).toBeDefined();
-      expect(
-        parsed.mcpServers.github_inline_comment.env.GITHUB_TOKEN,
-      ).toBe("test-token");
+      expect(parsed.mcpServers.github_inline_comment.env.GITHUB_TOKEN).toBe(
+        "test-token",
+      );
     });
   });
 });