[T4rk1n]

Sets up the next + dev workflow from RFD #142 (Dash release management: a next branch alongside dev). Fixes and chores target dev and ship as patches; features target next and ship as minors.

Already done outside this PR: next created from dev at 4.5.0 (00b8ed6), with a ruleset requiring a PR, one code-owner review, merge commits only, and the checks Consolidated Test Report, percy/dash-table-test, Forward merge not conflicted. Before merging: add the write deploy key, the DEV_NEXT_MERGE_KEY secret, and the DeployKey bypass on the next ruleset.

Changes

• forward-merge.yml: on each push to dev, merges dev into next and pushes it with the DEV_NEXT_MERGE_KEY deploy key. The deploy key and admins are the only actors allowed to bypass the next ruleset. If the merge conflicts, it opens a "Merge dev into next" PR from dev-into-next instead, and automatic merges pause until that PR is merged. It posts the Forward merge not conflicted status on that PR itself, because PRs opened with GITHUB_TOKEN do not trigger workflows.
• branch-policy.yml:
  • "No features on dev" fails PRs into dev that add an Unreleased Added CHANGELOG entry.
  • "Forward merge not conflicted" fails PRs into next while the forward PR has conflicts.
• testing.yml: runs on push to next; workflow_dispatch now runs the full suite.
• CONTRIBUTING.md, the PR template and CLAUDE.md explain which branch to target and the release steps; .ai/PERFORMANCE.md covers per-branch benchmark baselines.

Not verified yet

• Percy only auto-approves builds on configured branches, so visual diffs on next / dev-into-next may need manual approval.

Tested locally: the changelog script on fix, feature, old-style heading and existing-entry cases, and the forward-merge script against a local bare repo for each branch state (already merged, clean automatic merge, push race with another merge into next, conflict opening a PR, new fixes while that PR is open, resolved branch with a clean or conflicting fix). Not tested in a running Dash app: no Dash runtime behavior changes.

[sonarqubecloud]

Quality Gate passed

Issues
2 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