v0.8.67 Setup: remove deprecated WHALE.md discovery and docs surface

[Hmbown]

Maintainer direction

WHALE.md should stop being an active CodeWhale instruction surface in v0.8.67. It was already deprecated when .codewhale/constitution.json and AGENTS.md split the old responsibilities:

• ordinary project working guidance belongs in AGENTS.md,
• repo-local CodeWhale authority policy belongs in .codewhale/constitution.json,
• user-global standing behavior belongs in the global constitution setup flow,
• WHALE.md should not be generated, recommended, or silently treated as current law.

This issue owns removing the remaining compatibility/discovery path and cleaning up docs/copy so the setup lane has one clear model.

Desired behavior

• CodeWhale no longer discovers or loads project WHALE.md or global WHALE.md as default context.
• /init continues to create or update only AGENTS.md and never suggests WHALE.md.
• Existing docs explain the migration path once: move project instructions to AGENTS.md; move CodeWhale-specific repo authority policy to .codewhale/constitution.json.
• Context reports, doctor/setup output, README/config docs, and tests stop presenting WHALE.md as an active surface.
• If a transitional warning is retained, it should be explicit and finite: WHALE.md is ignored and should be migrated, not read as fallback law.

Acceptance criteria

• PROJECT_CONTEXT_FILES and global context discovery no longer include WHALE.md fallbacks.
• Tests that assert legacy WHALE.md loading are removed or rewritten to assert ignore/migration behavior.
• docs/CONFIGURATION.md, README copy, and context docs no longer describe WHALE.md as a read fallback.
• /init and generated .gitignore behavior still preserve .codewhale/constitution.json as the committable repo-local authority file.
• Release/setup docs include a concise migration note for users who still have WHALE.md.

Related

• Setup epic: v0.8.67 EPIC: Constitution-first setup wizard and user-global constitution #3402
• Constitution creator: v0.8.67 Setup: build a guided localized constitution creator, not a blank prompt editor #3793
• Constitution update checkpoint: v0.8.67 Setup: require a localized constitution checkpoint after update #3794
• Setup docs/localization: v0.8.67 Docs: constitution-first setup, localization, screenshots, and copy #3412