docs: fix broken PRP-0/INITIAL-0 relative links in 0-INIT_PHASE.md

[w7-mgfcode]

The repo-visibility audit found two broken relative links in docs/PHASE/0-INIT_PHASE.md:

• Line 577 — [PRP-0](../PRPs/PRP-0-project-foundation.md) resolves to docs/PRPs/... (missing)
• Line 578 — [INITIAL-0](../INITIAL-0.md) resolves to docs/INITIAL-0.md (missing)

Both need ../../ (repo root), not ../. Every other PHASE doc already uses ../../ for PRP/INITIAL links — 0-INIT_PHASE.md is the lone offender.

[w7-mgfcode]

Resolved — merged into dev (PR #137 / #139). Auto-close did not fire because the PRs targeted dev, not the default branch.