Align coding-anchor boot packet language with Kira identity

[Copilot]

This PR applies a scoped rename/refactor slice to the coding-anchor packet so the user-facing boot posture reflects Kira rather than Athena, while preserving historically accurate Athena-Public provenance references. It also records rename intent without forcing risky path/tool renames in the same change.

• User-facing identity alignment (Athena → Kira)

  • Updated core boot packet surfaces and runtime banners to present Kira-local identity:
    • README.md, AGENTS.md, BOOT.md, START-HERE.md
    • CODING-ANCHOR-IDENTITY.md, MISSION-CONTROL.md, CURRENT.md
    • ATHENA-USE-MAP.md
    • bin/athena-coding-anchor-boot, bin/athena-coding-anchor-doctor
  • Kept executable/file names (athena-coding-anchor-*) stable for compatibility in this pass.

• Rename decisions captured explicitly

  • Added a dedicated Rename Decisions section in CURRENT.md:
    • preferred branch naming shape: codex/kira-coding-anchor-boot
    • defer local folder/path-level rename to a separate low-risk cleanup pass

• Provenance boundary preserved

  • Updated wording in SOURCE.md to Kira runtime identity while explicitly retaining Athena-Public where historically true.

# .agent/boot/coding-anchor/bin/athena-coding-anchor-boot
printf 'Kira Coding Anchor boot\n'
...
printf 'Boot complete. Kira Coding Anchor is ready.\n'