docs: align process worktree delivery

[sabbour]

Summary

This change documents and aligns the delivery process for parallel implementation work:

• Requires dedicated clean worktrees for implementation and parallel streams.
• Makes the root checkout coordination-only when it is dirty or diverged.
• Requires pre-dispatch checks for model, ceremony, and worktree readiness.
• Requires agents to commit their work and then open draft pull requests.
• Scopes full ceremonies to substantial design work rather than routine delivery.
• Replaces repeated charter lockout with one fresh context that may reuse the same charter.

Focused review and diff checks were performed against the delivery branch. This is a draft PR for review only; no merge or post-creation edits are included.

Validation

• Worktree verified clean.
• Branch verified at 1f7edeff95b45ad82980dc29bd4a0e13681c7bfd before push.
• Diff checked against dev.