docs(pi): tighten support guidance

README.md

@@ -93,7 +93,7 @@ All 27 diagrams ship in three variants: minimal light, minimal dark, and full-ed
 pi install https://github.com/cathrynlavery/diagram-design
 ```
 
-Run `/reload` in an open Pi session. The skill activates automatically for diagram requests; use `/skill:diagram-design` to invoke it explicitly. Pi also loads the `/export-diagram` prompt template.
+Run `/reload` in an open Pi session. Pi makes the skill available for matching diagram requests; use `/skill:diagram-design` to invoke it explicitly. Pi also loads the `/export-diagram` prompt template.
 
 **Claude Code:**
 

prompts/export-diagram.md

@@ -26,5 +26,6 @@ Full argument string: `$ARGUMENTS`
 3. Source lacks `<svg>` → refuse; write nothing.
 4. PNG requested without Playwright → show install instruction from reference verbatim; stop. Do not auto-install.
 5. `--scale` outside {1, 2, 3} → reject.
+6. Both `--svg-only` and `--png-only` supplied → reject them as mutually exclusive.
 
 After export, report output paths plus sizes.

skills/diagram-design/references/onboarding.md

@@ -159,7 +159,7 @@ Use the installed-skill location exposed by the current agent when available. Ot
 **Pi:**
 
 1. `~/.pi/agent/skills/<skill-name>/` and `~/.agents/skills/<skill-name>/` (user installs)
-2. `.pi/skills/<skill-name>/` and `.agents/skills/<skill-name>/` from the current directory through the repo root (project installs)
+2. `.pi/skills/<skill-name>/` in the current directory, plus `.agents/skills/<skill-name>/` from the current directory through the repo root (project installs)
 3. Package paths listed in `~/.pi/agent/settings.json` or `.pi/settings.json`; managed packages live under `~/.pi/agent/git/`, `~/.pi/agent/npm/`, `.pi/git/`, or `.pi/npm/`
 
 **Claude Code:**