[AAASM-5047] 🐛 (docs-hub): Pin core module ref to main

[Chisanan232]

What

Pins the core (agent-assembly) module in modules.json from ref: "master" to ref: "main", matching the other three SDK modules. Also updates the accompanying channel description prose that referenced "master HEAD" to "main HEAD". No other entries touched.

Why

agent-assembly renamed its default branch master → main on 2026-07-23. The docs-hub Aggregate CI (aggregate.yml) clones each module at its pinned ref; the stale master pin makes git clone -b master fail with pathspec 'master' did not match, breaking the Aggregate job on every docs PR and the scheduled main run. Consequence: no aggregated Pages deploy has shipped since 2026-07-23.

The fix already existed as commit bc78d6f37, stranded on unrelated PR #131; this PR cherry-picks it onto its own branch so it can land independently.

How verified

• python3 -m json.tool modules.json → valid JSON
• Every module ref is now main (core, python-sdk, node-sdk, go-sdk, arena)
• grep master modules.json → only the generic $comment prose ("master/main HEAD") remains; no ref field references master

Jira

https://lightning-dust-mite.atlassian.net/browse/AAASM-5047

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Chisanan232]

🔎 Claude Code review — evidence for maintainer

CI state: Green. All 3 checks pass — SonarCloud (pass), Aggregate all module docs (pass), hub component metadata (pass). The Aggregate job is the one that was failing on every run before this change; it now completes, confirming the stale master pin was the cause.

Scope vs ticket (AAASM-5047): Exactly as scoped. One file, modules.json, 2 lines changed, both inside the core entry: ref master→main, and the channel prose that also read "master HEAD"→"main HEAD". Cherry-pick of the pre-existing fix bc78d6f37 (stranded on PR #131), so authorship is preserved. No other module entries, no other files.

Side-effects: None beyond intended. The other four modules were already on main. The lone remaining "master" token is generic descriptive text in the top-level $comment ("master/main HEAD"), not a ref — deliberately left untouched to keep the change minimal.

Two-party review: evidence only. Not an approval; not self-merged.

[Chisanan232]

✅ Claude Code review — READY (maintainer evidence)

1. CI: 3p/0f, SonarCloud PASS. Aggregate-docs job (was failing on the master pathspec) now green — the regression is resolved.
2. Sonar/CodeCov: no issues.
3. Scope (AAASM-5047): modules.json core entry ref+channel master→main via cherry-pick of the stranded bc78d6f37; all 5 module refs now main. Complete.
4. Side-effects: none — single data file, valid JSON, other modules untouched.
5. FE: none.

Verdict: scope-complete, MERGEABLE. Merge before #133 (its gate stacks on this). Evidence only — not an approval, not self-merged.