feat(commands): wire before/after hook events into specify and plan templates (#1886)

* feat(commands): wire before/after hook events into specify and plan templates

Replicates the hook evaluation pattern from tasks.md and implement.md
(introduced in PR #1702) into the specify and plan command templates.
This completes the hook lifecycle across all SDD phases.

Changes:
- specify.md: Add before_specify/after_specify hook blocks
- plan.md: Add before_plan/after_plan hook blocks
- EXTENSION-API-REFERENCE.md: Document new hook events
- EXTENSION-USER-GUIDE.md: List all available hook events

Fixes #1788

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

* Mark before_commit/after_commit as planned in extension docs

These hook events are defined in the API reference but not yet wired
into any core command template. Marking them as planned rather than
removing them, since the infrastructure supports them.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Fix hook enablement to default true when field is absent

Matches HookExecutor.get_hooks_for_event() semantics where
hooks without an explicit enabled field are treated as enabled.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(docs): mark commit hooks as planned in user guide config example

The yaml config comment listed before_commit/after_commit as
"Available events" but they are not yet wired into core templates.
Moved them to a separate "Planned" line, consistent with the
API reference.

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

* fix(commands): align enabled-filtering semantics across all hook templates

tasks.md and implement.md previously said "Filter to only hooks where
enabled: true", which would skip hooks that omit the enabled field.
Updated to match specify.md/plan.md and HookExecutor's h.get('enabled', True)
behavior: filter out only hooks where enabled is explicitly false.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

extensions/EXTENSION-API-REFERENCE.md

@@ -53,7 +53,7 @@ provides:
       required: boolean  # Default: false
 
 hooks:                   # Optional, event hooks
-  event_name:            # e.g., "after_tasks", "after_implement"
+  event_name:            # e.g., "after_specify", "after_plan", "after_tasks", "after_implement"
     command: string      # Command to execute
     optional: boolean    # Default: true
     prompt: string       # Prompt text for optional hooks
@@ -108,7 +108,7 @@ defaults:                # Optional, default configuration values
 #### `hooks`
 
 - **Type**: object
-- **Keys**: Event names (e.g., `after_tasks`, `after_implement`, `before_commit`)
+- **Keys**: Event names (e.g., `after_specify`, `after_plan`, `after_tasks`, `after_implement`, `before_commit`)
 - **Description**: Hooks that execute at lifecycle events
 - **Events**: Defined by core spec-kit commands
 
@@ -551,10 +551,16 @@ hooks:
 
 Standard events (defined by core):
 
+- `before_specify` - Before specification generation
+- `after_specify` - After specification generation
+- `before_plan` - Before implementation planning
+- `after_plan` - After implementation planning
+- `before_tasks` - Before task generation
 - `after_tasks` - After task generation
+- `before_implement` - Before implementation
 - `after_implement` - After implementation
-- `before_commit` - Before git commit
-- `after_commit` - After git commit
+- `before_commit` - Before git commit *(planned - not yet wired into core templates)*
+- `after_commit` - After git commit *(planned - not yet wired into core templates)*
 
 ### Hook Configuration