docs: Provide ACP workflow example in README.md

feat(commands): add Step 0 command header to all 46 commands — display purpose, usage, and related commands on invocation

docs(commands): add Step 0 command header to template, refactor proceed --worktrees as opt-in

feat(index): implement path: null inline entries with kind: note and kind: directive — M18 complete (Task 120)

plan(M18): create milestone and task-120 for index semantic entry types — path: null inline notes and directives

feat(design): create index semantic entry types design — path: null for inline notes and directives (clarification-13)

docs(proceed): add --safe flag aliases, directive header, and Example 7 for worktree merge gating

docs(proceed): add --noworktreemerge/--safe flag for gated worktree merging in parallel autonomous mode

fix(project-update): fix duplicate tag detection — yaml_query can't read array items, use raw grep instead

feat(ci): add GitHub Actions E2E workflow for ubuntu + macos matrix — M13 Cross-Platform CI complete (Task 98, M13)

feat(ci): add unified E2E test runner run-e2e-tests.sh — discover, run, report all test suites (Task 97, M13)

fix(e2e): fix macOS compatibility in E2E tests — portable sed, date, exit codes (Task 96, M13)

fix(proceed): harden @acp.proceed to aggressively set timestamps and status on tasks and milestones — mandatory start/end dates, milestone in_progress/completed transitions, auto-advance current_milestone

version: bump ACP 5.28.4, package 4.6.3, progress 6.0.3 — auto-commit for creation commands

version: bump ACP 5.28.3, package 4.6.2, progress 6.0.2 — priority numeric migration