refactor: remove agent triggers config field (#469)

* refactor: remove agent triggers config field

Remove the triggers field from agent configuration. The on_assign,
on_comment, and on_mention behaviors are now always enabled (hardcoded),
as decided in the Agentflow design discussion (MUL-372).

Changes:
- Database: migration 032 drops triggers column from agent table
- Backend: remove triggers from create/update agent APIs and response
- Backend: simplify trigger-checking logic to always-enabled
- Frontend: remove TriggersTab UI and AgentTrigger types
- Tests: remove trigger config unit tests (no longer configurable)

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

* refactor: also remove agent tools config field

Remove the tools field from agent configuration alongside triggers.
The tools field was a placeholder — stored in the DB and shown in the
UI but never passed to the daemon or used at runtime.

- Database: migration 032 now also drops tools column
- Backend: remove tools from create/update agent APIs and response
- Frontend: remove ToolsTab UI, AgentTool type, and tools tab
- Update landing page copy

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

* fix(test): remove tools/triggers columns from test fixtures

The test fixtures still referenced the dropped tools and triggers
columns when inserting agent rows, causing CI failures.

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

---------

Co-authored-by: Devv <devv@Devvs-Mac-mini.local>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/pkg/db/queries/agent.sql

@@ -20,8 +20,8 @@ WHERE id = $1 AND workspace_id = $2;
 INSERT INTO agent (
     workspace_id, name, description, avatar_url, runtime_mode,
     runtime_config, runtime_id, visibility, max_concurrent_tasks, owner_id,
-    tools, triggers, instructions
-) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13)
+    instructions
+) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11)
 RETURNING *;
 
 -- name: UpdateAgent :one
@@ -35,8 +35,6 @@ UPDATE agent SET
     visibility = COALESCE(sqlc.narg('visibility'), visibility),
     status = COALESCE(sqlc.narg('status'), status),
     max_concurrent_tasks = COALESCE(sqlc.narg('max_concurrent_tasks'), max_concurrent_tasks),
-    tools = COALESCE(sqlc.narg('tools'), tools),
-    triggers = COALESCE(sqlc.narg('triggers'), triggers),
     instructions = COALESCE(sqlc.narg('instructions'), instructions),
     updated_at = now()
 WHERE id = $1