fix(docs): collapse three org-level security placeholder names into one

[AmirF194]

Summary

• The org-level advisory-admin security address had three names in the tree (<security-team-list>, <asf-security-list>, and the bare security_inbox.foundation_security_address config path) and none was registered in the placeholder table.
• <asf-security-list> also bakes an ASF-specific name into a framework whose placeholder mechanism exists to keep adopting projects vendor-neutral.
• Registers one org-neutral placeholder, <foundation-security-list>, and uses it at all three call sites. The distinct project-level <security-list> is untouched, since github-advisory.md's own delivery instructions deliberately address the two lists separately.

Type of change

• Skill change (.claude/skills/<name>/) - eval fixtures updated below
• Tool / bridge contract (tools/<system>/*.md)
• Python package (tools/*/ with pyproject.toml)
• Groovy reference impl
• Cross-cutting (RFC, AGENTS.md, sandbox, privacy-LLM)
• Documentation (docs/, README.md, CONTRIBUTING.md)
• Project template (projects/_template/)
• CI / dev loop (prek, workflows, validators)
• Other:

Test plan

• prek run --all-files not available in this environment (no uv/prek); ran the individual hooks by hand instead: tools/dev/check-placeholders.sh, npx markdownlint-cli2 and typos on both changed files, and the doctoc check (no TOC change needed; skills/** is excluded from the doctoc hook and AGENTS.md's TOC is unaffected by a text-only edit). All clean.
• PYTHONPATH=tools/skill-and-tool-validator/src python3 -c "from skill_and_tool_validator import main; main()" (the same entry point uv run skill-and-tool-validate calls) reports the same 29 pre-existing soft warnings before and after this change, none on the touched files.
• Other: did not run the Python test matrix; this PR touches no tools/*/ package.

RFC-AI-0004 compliance

• HITL - any new mutation is gated on explicit user confirmation
• Sandbox - no new unrestricted host access; network reach declared in the adapter
• Vendor neutrality - replaces an ASF-branded placeholder (<asf-security-list>) with an org-neutral one, matching <governance-body> and <project-stage>
• Conversational + correctable - agentic-override path documented if behaviour is adopter-tunable
• Write-access discipline - no autonomous outbound messages; drafts only, sent on confirmation
• Privacy LLM - private content does not reach a non-approved LLM; redactor invoked where needed

Linked issues

Fixes #1057

Notes for reviewers (optional)

Followed the naming this issue itself suggests, matching the config key: <foundation-security-list> rather than <org-security-list>. projects/_template/project.md already documents security_inbox.foundation_security_address as org-level and inherited ("Do not declare it here"), so no change was needed there.

[onlyarnav]

LGTM

Ready to merge.

[AmirF194]

Good, that closes out the placeholder collapse cleanly.