Update all master branch references to main (#2676)

Closes #2659

The default branch was renamed from `master` to `main` on GitHub. This
PR updates all code references to match.

- **CI workflows**: All 15 workflow files updated — branch triggers,
`BASE_REF`/`BASE_SHA` fallbacks, `refs/heads/` conditions, and comments
- **GitHub Action**: Renamed `ensure-master-docs-safety` →
`ensure-main-docs-safety` (directory + content)
- **Documentation**: ~50 files with GitHub URLs updated from
`/blob/master/` and `/tree/master/` to `/main/`
- **Config files**: Coveralls badge URLs, package.json homepage, rakelib
comments, CLAUDE.md/AGENTS.md references

- [ ] CI workflows trigger correctly on pushes to `main`
- [ ] `detect-changes` fallback uses `origin/main` correctly
- [ ] `ensure-main-docs-safety` action runs on docs-only pushes
- [ ] Benchmark workflow references `main` for Bencher branch tracking
- [ ] Documentation links resolve correctly

🤖 Generated with [Claude Code](https://claude.com/claude-code)

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Medium risk because it touches many GitHub Actions workflows and CI
guard logic; a missed branch/ref update could cause workflows not to
trigger or docs-only pushes to incorrectly skip CI.
>
> **Overview**
> Updates the repo-wide default-branch assumption from `master` to
`main`, including documentation links/badges, contributor guidance, and
changelog compare URLs.
>
> Adjusts CI to run against `main`: workflow push triggers and
`refs/heads/*` conditions are switched, docs-only safeguards now use a
renamed `ensure-main-docs-safety` composite action, and tooling
defaults/fallbacks (e.g., `script/ci-changes-detector`, `bin/ci-local`,
actionlint base ref) now compare against `origin/main`.
>
> Updates release/changelog automation to treat `main` as the required
stable release branch and to generate compare links targeting `...main`
(with specs updated accordingly).
>
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
1514d64. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

* **Chores**
* Switched default branch references from "master" to "main" across
CI/workflows, scripts, tooling, and release checks so triggers and
defaults target main.
* **Documentation**
* Updated links, examples, badges, guides, and contributor/release
instructions to reference the main branch throughout docs and READMEs.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: justin808

.claude/agents/pr-testing-agent.md

@@ -14,7 +14,7 @@ description: Validates PR testing before merge. Use when creating PRs, investiga
 When you need more details, use the Read tool to examine:
 
 - `.claude/docs/testing-build-scripts.md` - Build/package testing requirements
-- `.claude/docs/master-health-monitoring.md` - Post-merge CI monitoring
+- `.claude/docs/main-health-monitoring.md` - Post-merge CI monitoring
 - `SWITCHING_CI_CONFIGS.md` - CI config switching guide
 - `react_on_rails/spec/dummy/TESTING_LOCALLY.md` - Environment-specific testing issues
 

.claude/docs/analysis/INDEX.md

@@ -108,7 +108,7 @@ Outside the analysis directory:
 - **Main Migration Plan**: `/docs/MONOREPO_MERGER_PLAN.md` (authoritative source)
 - **Path Management Guide**: `/.claude/docs/managing-file-paths.md` (validation procedures)
 - **Build Script Testing**: `/.claude/docs/testing-build-scripts.md` (artifact verification)
-- **CI Monitoring**: `/.claude/docs/master-health-monitoring.md` (CI status checks)
+- **CI Monitoring**: `/.claude/docs/main-health-monitoring.md` (CI status checks)
 - **Contributing Guide**: `/CONTRIBUTING.md` (developer instructions)
 
 ---
@@ -195,7 +195,7 @@ Outside this analysis directory:
 - **Main Migration Plan**: `/docs/MONOREPO_MERGER_PLAN.md` (authoritative source)
 - **Path Management Guide**: `/managing-file-paths.md` (validation procedures)
 - **Build Script Testing**: `/testing-build-scripts.md` (artifact verification)
-- **CI Monitoring**: `/master-health-monitoring.md` (CI status checks)
+- **CI Monitoring**: `/main-health-monitoring.md` (CI status checks)
 - **Contributing Guide**: `/CONTRIBUTING.md` (developer instructions)
 
 ## Workflow Tips

.claude/docs/analysis/MONOREPO_MIGRATION_ANALYSIS.md

@@ -240,7 +240,7 @@ task node_package: "node_package:build"
 ```
 .conductor/surabaya-v1/.claude/docs/
 ├── testing-build-scripts.md      # Critical for path verification
-├── master-health-monitoring.md   # CI status checks
+├── main-health-monitoring.md     # CI status checks
 ├── managing-file-paths.md        # Path validation after refactors
 └── analysis/                     # Analysis documents
 ```

.claude/docs/analysis/README.md

@@ -26,7 +26,7 @@ These documents serve as:
 The analysis in these files led to the creation of:
 
 - `.claude/docs/testing-build-scripts.md`
-- `.claude/docs/master-health-monitoring.md`
+- `.claude/docs/main-health-monitoring.md`
 - `.claude/docs/managing-file-paths.md`
 
 See also PR #2062 and PR #2065 for the full context.

.claude/docs/avoiding-ci-failure-cycles.md

@@ -216,7 +216,7 @@ bin/ci-rerun-failures
 
 **IMPORTANT: Poll every 30 seconds, NOT 180 seconds.** CI jobs typically complete in 3-15 minutes, so 30-second polling gives responsive feedback.
 
-**See**: [master-health-monitoring.md](master-health-monitoring.md)
+**See**: [main-health-monitoring.md](main-health-monitoring.md)
 
 ## Red Flags: When to STOP and Test More
 
@@ -400,7 +400,7 @@ If the answer is **YES**, spend the 15 minutes.
 ## Related Documentation
 
 - [testing-build-scripts.md](testing-build-scripts.md) - Build script testing requirements
-- [master-health-monitoring.md](master-health-monitoring.md) - Post-merge monitoring
+- [main-health-monitoring.md](main-health-monitoring.md) - Post-merge monitoring
 - [pr-testing-agent.md](pr-testing-agent.md) - Comprehensive PR testing guide
 - [CLAUDE.md](../../CLAUDE.md) - Full development guide
 - [SWITCHING_CI_CONFIGS.md](../../SWITCHING_CI_CONFIGS.md) - Testing minimum vs latest

.claude/docs/master-health-monitoring.md

@@ -689,4 +689,4 @@ gh pr view --json statusCheckRollup
 - CI debugging: [CLAUDE.md](../../CLAUDE.md) "Replicating CI Failures Locally"
 - Config switching: [SWITCHING_CI_CONFIGS.md](../../SWITCHING_CI_CONFIGS.md)
 - Local testing issues: [react_on_rails/spec/dummy/TESTING_LOCALLY.md](../../react_on_rails/spec/dummy/TESTING_LOCALLY.md)
-- Master health: [master-health-monitoring.md](master-health-monitoring.md)
+- Main health: [main-health-monitoring.md](main-health-monitoring.md)

.claude/docs/pr-testing-guide.md

@@ -35,7 +35,7 @@ By default, PRs run a subset of CI jobs to provide fast feedback:
 - Skips example generator tests
 - Skips some Pro package tests
 
-This is intentional to keep PR feedback loops fast. However, before merging, you should verify compatibility across all supported versions. The `/run-skipped-ci` (or `/run-skipped-tests`) command makes this easy without waiting for the PR to be merged to master.
+This is intentional to keep PR feedback loops fast. However, before merging, you should verify compatibility across all supported versions. The `/run-skipped-ci` (or `/run-skipped-tests`) command makes this easy without waiting for the PR to be merged to main.
 
 ### Security & Access Control
 
@@ -53,13 +53,13 @@ Multiple `/run-skipped-ci` or `/run-skipped-tests` comments on the same PR will
 
 ## Testing Comment-Triggered Workflows
 
-**Important**: Comment-triggered workflows (`issue_comment` event) only execute from the **default branch** (master). This creates a chicken-and-egg problem when developing workflow changes.
+**Important**: Comment-triggered workflows (`issue_comment` event) only execute from the **default branch** (main). This creates a chicken-and-egg problem when developing workflow changes.
 
 ### Recommended Testing Approach
 
 1. **Develop the workflow**: Create/modify the workflow in your feature branch
 2. **Test locally**: Validate YAML syntax and logic as much as possible
-3. **Merge to master**: The workflow must be in master to be triggered by comments
+3. **Merge to main**: The workflow must be in main to be triggered by comments
 4. **Test on a PR**: Create a test PR and use the comment command to verify
 
 ### Why This Limitation Exists
@@ -109,7 +109,7 @@ Most workflows use minimal permissions. The comment-triggered workflows require:
 
 Many workflows use change detection to skip unnecessary jobs:
 
-- Runs all jobs on pushes to `master`
+- Runs all jobs on pushes to `main`
 - Runs only relevant jobs on PRs based on changed files
 - Can be overridden with `workflow_dispatch` or `/run-skipped-ci` (or `/run-skipped-tests`) command