sessionStart  prompt hooks don't fire on  /new , and  /clear  seems to skip sessionStart entirely — naming/behavior mismatch

### Describe the feature or problem you'd like to solve

Invoke a skill foreach new session

### Proposed solution

The  **sessionStart**  hook name strongly implies it fires whenever a new "session" (conversation) begins — including via  /new  and  /clear . In practice:
1. Hook entries of  **"type": "prompt"**  only fire on true CLI process startup ( **source: "startup"** ), not on  /new  ( **source: "new"** ) or  /clear , per the docs note: "Prompt hooks fire only for new interactive sessions... They do not fire on resume." This is confusing because  /new  is documented as "Start a new conversation" and intuitively should count as a "new interactive session."
2.  /clear  ("Abandon this session and start fresh") doesn't appear to trigger  sessionStart  at all — it's not listed among the  source  values ( "startup" | "resume" | "new" ).

This creates a real usability gap: a user-level hook meant to re-apply a session-scoped customization (e.g., auto-running a skill/mode via a prompt hook) silently stops working after  /new  or  /clear , with no indication in  /env  that anything is "missing" — the hook config is loaded, it just never fires again for these transitions.

Suggestions:
• Either make  "type": "prompt"  hooks fire for  source: "new"  (matching user expectation and documented  /new  behavior), or rename the event/restrict the docs wording so it's unambiguous that  sessionStart  (for prompt hooks) really means "process startup only."
• Clarify/confirm whether  /clear  fires  sessionStart  at all, and add it explicitly to the  source  enum if so.
• Consider a distinct event (e.g.,  conversationStart ) for  /new / /clear  transitions, separate from true process-level  sessionStart , so hook authors can target the semantics they actually need.

### Example prompts or workflows

_No response_

### Additional context

_No response_

Commencez par la documentation du hook sessionStart et suivez la manière dont les commandes /new et /clear gèrent les sources des hooks. Confirmez le comportement actuel des hooks de prompt et définissez si ces transitions doivent utiliser sessionStart ou un événement distinct. Le travail est terminé lorsque la sémantique des événements, les valeurs des sources et la documentation sont cohérentes, et que les transitions concernées sont couvertes par des tests.

Rédigé par le modèle d'indexation à partir du texte de l'issue.