Update distill skill to target BESTPRACTICES.md instead of INDEX.md

Matches the move of best-practices/INDEX.md to BESTPRACTICES.md in
claude-foundations root for context-load auto-discovery.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

skills/distill-best-practices/SKILL.md

@@ -21,7 +21,7 @@ You are extracting generalisable best practices from project-specific memory fil
 !`cat ~/dev/claude/projects/claude-foundations/settings.yaml 2>/dev/null || echo "No settings file found"`
 
 ### Current best-practices index
-!`cat ~/dev/claude/projects/claude-foundations/best-practices/INDEX.md 2>/dev/null || echo "No index found"`
+!`cat ~/dev/claude/projects/claude-foundations/BESTPRACTICES.md 2>/dev/null || echo "No index found"`
 
 ### Available best-practices files
 !`ls -1 ~/dev/claude/projects/claude-foundations/best-practices/ 2>/dev/null || echo "No best-practices directory"`
@@ -106,7 +106,7 @@ For each approved proposal:
 
 If a new best-practices topic file is needed:
 - Create it following the format of existing files (top-level heading, subheadings per entry, 2-6 lines per entry)
-- Add it to `INDEX.md` with a one-line description
+- Add it to `BESTPRACTICES.md` (in the claude-foundations project root) with a one-line description
 
 ### Step 6: Update distill state
 
@@ -141,5 +141,5 @@ Print:
 - Best practices must be **project-agnostic** — no hardcoded IPs, namespaces, or service names
 - Each entry should include the **principle and reasoning**, not just the rule
 - Entries must be **deduplicated** against existing best-practices content
-- The **INDEX.md** must stay accurate after any file additions
+- The **BESTPRACTICES.md** must stay accurate after any file additions
 - Proposals are **always presented before applying** — never auto-apply