fix: address review findings on formula templates and BOOTSTRAP docs

- upgrade-dependency.toml: fix forge upgrade command (forge update, not
  forge install); remove redundant `npm install` after lockfile write;
  simplify description to "Upgrade {{package}} to {{to_version}}" so it
  reads cleanly when from_version is omitted
- add-rpc-method.toml: remove dead `namespace` variable; inline namespace
  derivation logic into register-method step description
- BOOTSTRAP.md: mark formula label entry as requiring feat/formula merge;
  add YAML front matter example so operators know the issue schema

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

BOOTSTRAP.md

@@ -84,7 +84,7 @@ Optional but recommended:
 |-------|---------|
 | `tech-debt` | Gardener can promote these to `backlog` |
 | `blocked` | Dev-agent marks issues with unmet dependencies |
-| `formula` | Dev-agent uses a structured TOML formula instead of freeform — issue body must have YAML front matter specifying the formula name and variables (see `formulas/`) |
+| `formula` | *(requires `feat/formula` merge)* Dev-agent uses a structured TOML formula instead of freeform. Issue body must include YAML front matter, e.g.:<br>`---`<br>`formula: upgrade-dependency`<br>`vars:`<br>`  package: viem`<br>`  ecosystem: npm`<br>`---` |
 
 ### Required: Branch protection