feat: Add hooks, steering, and skills system with multi-tool integration

Add lifecycle hooks, steering files, and skills packages with full
convention alignment to main's audit and compliance requirements.

Key additions:
- Hook discovery, runner, and security validation (internal/hook/)
- Steering file parser, sync engine, and filter (internal/steering/)
- Skill install, load, and remove (internal/skill/)
- CLI commands: ctx hook, ctx steering, ctx skill
- Setup support for Cursor, Kiro, and Cline
- MCP steering search tool
- Drift checks for steering sync staleness

Convention alignment:
- All fmt.Errorf moved to internal/err/ helpers
- All cmd.Println/Printf moved to internal/write/ helpers
- All raw file I/O replaced with internal/io/Safe* wrappers
- All bare err := renamed to descriptive names
- All flag bindings use flagbind.* helpers
- exec.CommandContext moved to internal/exec/hook/
- Magic strings/numbers replaced with config constants
- Line length, doc comments, mixed visibility fixes

Signed-off-by: Murat Parlakisik <parlakisik@gmail.com>

Author: parlakisik

.kiro/specs/hooks-and-steering/.config.kiro

@@ -0,0 +1 @@
+{"specId": "2f530946-c219-4541-8a51-b532a017ae47", "workflowType": "requirements-first", "specType": "feature"}