fix: Commit embedded formulas for go install @latest (#117)

* fix: Commit embedded formulas for go install @latest

The internal/formula/formulas/ directory was gitignored, causing
`go install github.com/steveyegge/gastown/cmd/gt@latest` to fail with:

  pattern formulas/*.formula.json: no matching files found

The go:embed directive requires these files at build time, but
go install @latest doesn't run go:generate. By committing the
generated formulas, users can install directly without cloning.

Maintainers should run `go generate ./...` after modifying
.beads/formulas/ to keep the embedded copy in sync.

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

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

* ci: Add check for committed embedded formulas

Adds a new CI job that:
1. Builds without running go:generate (catches missing formulas)
2. Verifies committed formulas match .beads/formulas/ source

Also removes redundant go:generate steps from other jobs since
formulas are now committed.

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

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

* chore: exclude towers-of-hanoi test formulas from embed

These are durability stress test fixtures (pre-computed move sequences),
not production formulas users need. Excluding them reduces embedded
content by ~10K lines.

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

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

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: gus <steve.yegge@gmail.com>

.gitignore

@@ -34,5 +34,5 @@ state.json
 # Clone-specific CLAUDE.md (regenerated locally per clone)
 CLAUDE.md
 
-# Generated by go:generate from .beads/formulas/
-internal/formula/formulas/
+# Embedded formulas are committed so `go install @latest` works
+# Run `go generate ./...` after modifying .beads/formulas/