Migrate GitHub teams to infrastructure-as-code (#5)

* Migrate GitHub teams to infrastructure-as-code

- Add 25 teams with proper hierarchy (steering-committee, SDK teams, working groups, interest groups)
- Add 67 team members with their assignments
- Add repository access configuration for all 21 repositories
- Refactor github.ts to use config-driven approach with repoAccess.ts
- Mark all MCP teams as GitHub-only with onlyOnPlatforms
- Use RepositoryCollaborators for authoritative access management

Note: GitHub Projects V2 permissions are not yet supported by Pulumi and must be managed manually. See https://github.com/pulumi/pulumi-github/issues/1006

* Add individual user collaborators to repository access

Preserves direct collaborator access for users who have explicit permissions outside of team membership, including:
- jspahrsummers: admin on multiple core repos
- Go SDK collaborators (neild, rsc, rolandshoemaker, h9jiang)
- C# SDK collaborators (jeffhandley, MackinnonBuck, jozkee, localden, PederHP)
- Rust SDK collaborators (jamadeo, jokemanfire, 4t145)
- Inspector collaborators (richardkmichael, olaservo, an-dustin, ashwin-ant)
- Financial services IG collaborators (aniabot, imfing, sambhav, KengoA, nitsanh)
- And others

Without this, RepositoryCollaborators (authoritative mode) would remove all individual user access.

src/github.ts

@@ -1,5 +1,6 @@
 import * as github from '@pulumi/github';
 import { GROUPS } from './config/groups';
+import { REPOSITORY_ACCESS } from './config/repoAccess';
 import type { Group } from './config/utils';
 import { MEMBERS } from './config/users';
 
@@ -28,3 +29,17 @@ MEMBERS.forEach((member) => {
     });
   });
 });
+
+REPOSITORY_ACCESS.forEach((repo) => {
+  new github.RepositoryCollaborators(`repo-${repo.repository}`, {
+    repository: repo.repository,
+    teams: repo.teams?.map((t) => ({
+      teamId: teams[t.team].id,
+      permission: t.permission,
+    })),
+    users: repo.users?.map((u) => ({
+      username: u.username,
+      permission: u.permission,
+    })),
+  });
+});