docs: Clarify formula vs molecule semantics - formulas are NOT instructions

PROBLEM: Agents were reading formula files directly and manually creating beads
for each step, rather than using the cook→pour→molecule pipeline.

FIXES:
- polecat-CLAUDE.md: Changed "following the formula" to "work through your
  pinned molecule" and added explicit anti-pattern warning
- mol-polecat-work.formula.toml: Added note that formula defines template,
  use bd ready to find step beads
- docs/molecules.md: Added "Common Mistake" section with WRONG/RIGHT examples
- mol-*.formula.toml (5 files): Changed "execute this formula" to "work
  through molecules (poured from this formula)"

The key insight: Formulas are source templates (like source code). You never
read them directly. The cook → pour pipeline creates step beads for you.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.beads/formulas/mol-session-gc.formula.toml

@@ -1,7 +1,7 @@
 description = """
 Clean stale sessions and garbage collect.
 
-Dogs execute this formula to clean up dead sessions, orphaned processes, and
+Dogs work through molecules (poured from this formula) to clean up dead sessions, orphaned processes, and
 other system cruft. This is the garbage collector for Gas Town's runtime:
 - Dead tmux sessions (no Claude process)
 - Orphaned Claude processes (no tmux parent)