docs(agents): clarify branch lifecycle and worktree workflow (#344)

AGENTS.md

@@ -172,6 +172,27 @@ When uncertain, classify as higher risk.
     - If stacked PR: declare `Depends on #...`.
     - If replacing old PR: declare `Supersedes #...`.
 
+### 6.3 Branch / Commit / PR Flow (Required)
+
+All contributors (human or agent) must follow the same collaboration flow:
+
+- Create and work from a non-`main` branch.
+- Commit changes to that branch with clear, scoped commit messages.
+- Open a PR to `main`; do not push directly to `main`.
+- Wait for required checks and review outcomes before merging.
+- Merge via PR controls (squash/rebase/merge as repository policy allows).
+- Branch deletion after merge is optional; long-lived branches are allowed when intentionally maintained.
+
+### 6.4 Worktree Workflow (Required for Multi-Track Agent Work)
+
+Use Git worktrees to isolate concurrent agent/human tracks safely and predictably:
+
+- Use one worktree per active branch/PR stream to avoid cross-task contamination.
+- Keep each worktree on a single branch; do not mix unrelated edits in one worktree.
+- Run validation commands inside the corresponding worktree before commit/PR.
+- Name worktrees clearly by scope (for example: `wt/ci-hardening`, `wt/provider-fix`) and remove stale worktrees when no longer needed.
+- PR checkpoint rules from section 6.3 still apply to worktree-based development.
+
 ### 6.1 Code Naming Contract (Required)
 
 Apply these naming rules for all code changes unless a subsystem has a stronger existing pattern.
@@ -237,6 +258,17 @@ cargo clippy --all-targets -- -D warnings
 cargo test
 ```
 
+Preferred local pre-PR validation path (recommended, not required):
+
+```bash
+./dev/ci.sh all
+```
+
+Notes:
+
+- Local Docker-based CI is strongly recommended when Docker is available.
+- Contributors are not blocked from opening a PR if local Docker CI is unavailable; in that case run the most relevant native checks and document what was run.
+
 Additional expectations by change type:
 
 - **Docs/template-only**: run markdown lint and relevant doc checks.