Revert "feat: skill prerequisites — hide skills with unmet runtime dependencies"

CONTRIBUTING.md

@@ -328,11 +328,6 @@ license: MIT
 platforms: [macos, linux]          # Optional — restrict to specific OS platforms
                                    #   Valid: macos, linux, windows
                                    #   Omit to load on all platforms (default)
-prerequisites:                     # Optional — runtime requirements
-  env_vars: [MY_API_KEY]           #   Env vars that must be set
-  commands: [curl, jq]             #   CLI binaries that must be on PATH
-                                   #   Skills with unmet prerequisites are hidden
-                                   #   from the system prompt and flagged in skill_view.
 metadata:
   hermes:
     tags: [Category, Subcategory, Keywords]
@@ -371,25 +366,6 @@ platforms: [windows]          # Windows only
 
 If the field is omitted or empty, the skill loads on all platforms (backward compatible). See `skills/apple/` for examples of macOS-only skills.
 
-### Skill prerequisites
-
-Skills can declare runtime prerequisites via the `prerequisites` frontmatter field. Skills with unmet prerequisites are automatically hidden from the system prompt (the agent won't claim it can use them) and show a clear warning in `skill_view()` telling the agent what's missing.
-
-```yaml
-prerequisites:
-  env_vars: [TENOR_API_KEY]       # Env vars checked via os.getenv()
-  commands: [curl, jq]            # CLI binaries checked via shutil.which()
-```
-
-Both sub-fields are optional — declare only what applies. If the field is omitted entirely, the skill is always available (backward compatible).
-
-**When to declare prerequisites:**
-- The skill uses a CLI tool that isn't universally installed (e.g., `himalaya`, `openhue`, `ddgs`)
-- The skill requires an API key in the environment (e.g., `NOTION_API_KEY`, `TENOR_API_KEY`)
-- Without these, the skill's commands will fail — not just degrade gracefully
-
-See `skills/gifs/gif-search/` and `skills/email/himalaya/` for examples.
-
 ### Skill guidelines
 
 - **No external dependencies unless absolutely necessary.** Prefer stdlib Python, curl, and existing Hermes tools (`web_extract`, `terminal`, `read_file`).