[Bug]: cupcake validate flags valid decision verbs on Cursor (and other non-Claude) events

[chozandrias76]

Bug Description

The decision-event compatibility matrix (cupcake-core/src/validator/decision_event_matrix.rs) only contains Claude Code events. For any Cursor-native event (beforeShellExecution, afterFileEdit, beforeReadFile, …), compatible_verbs() returns an empty list, so is_compatible() returns false for every decision verb. As a result cupcake validate reports each verb on those events as incompatible with an empty Supported: list.

This makes the Cursor builtins that cupcake init generates fail validation out of the box. Swapping the verb (e.g. halt → deny) does not help, because no verb is registered for those events — the matrix simply has no entry for the event at all.

Steps to Reproduce

1. cupcake init --global --harness claude (this also scaffolds the cursor/builtins/*.rego policies)
2. cupcake validate --policy-dir ~/.config/cupcake/policies
3. Observe errors on the Cursor builtins, e.g.:

✗ .../policies/cursor/builtins/system_protection.rego
  ERROR (line 15): Policy routes to 'beforeShellExecution' events but uses incompatible 'halt' decision verb. 'halt' decisions are not supported for beforeShellExecution events. Supported: 
  ERROR (line 15): Policy routes to 'afterFileEdit' events but uses incompatible 'halt' decision verb. 'halt' decisions are not supported for afterFileEdit events. Supported: 

(The empty string after Supported: is the tell — the matrix has no entry for the event.)

Expected Behavior

Decision verbs that are valid for a harness's events should validate cleanly, and the validator should not flag events it has no spec for.

Actual Behavior

Every decision verb used on a Cursor-native event is reported as incompatible with an empty Supported: list, so cupcake validate fails on the generated Cursor builtins.

Harness

Cursor (note: validate applies the Claude-Code matrix regardless of which harness is active)

Cupcake Version

0.5.2

Operating System

Linux

OS Version

CachyOS (Arch-based)

Additional Context

Root cause: DecisionEventMatrix::new() only inserts Claude Code events; compatible_verbs() falls back to unwrap_or_default() (empty) for unknown events, and the compatibility rule in validator/rules.rs flags every verb against that empty set.

Proposed fix (PR incoming): add Cursor's actionable before/stop events to the matrix with verb sets derived from the Cursor response handlers (beforeShellExecution/beforeMCPExecution: halt/deny/block/ask; beforeReadFile and beforeSubmitPrompt: halt/deny/block; stop: halt/block); add a knows_event() helper; and have the rule skip events the matrix doesn't know — covering Cursor's fire-and-forget after* events and other harnesses' events — while still validating known-but-empty events like SessionEnd. Regression tests included.