feat(views): unify Edit Details and Quick Controls into Edit Task with draft UX

[espdesign]

Description

Consolidates the previously fragmented Edit Details (text modal) and Quick Controls (dropdowns panel) buttons on the Forum Task Thread Action Card into a single cohesive Edit Task interactive controls panel with clean Unsaved Draft UX styling.

Key Changes

• Action Card Button Consolidation: Replaced separate Edit Details and Quick Controls buttons on TaskActionView with a single Edit Task button (task:edit:{task_id}).
• Backward Compatibility: Updated DiscordTaskWorkspaceAdapter.handle_action so both task:edit and task:controls custom IDs route to the unified controls panel.
• Title & Description Editing: Added staged_title and staged_body staging to TaskQuickControlsView, with an Edit Title / Body modal button in Row 0 (TaskQuickEditTitleModal).
• Clean Draft UX:
  • Embed title: Edit Draft: [SHORT_ID] Title
  • Embed color: Amber/Gold (discord.Color.gold()) signaling an in-progress draft
  • Footer warning: ⚠️ Unsaved Draft • Click 'Save Changes' to apply or 'Discard Changes' to cancel.
  • Action buttons: Discard Changes with danger styling (discord.ButtonStyle.danger) next to Save Changes (discord.ButtonStyle.success).
• Atomic Save: _on_save_clicked commits all modified fields (title, description, priority, assignee, due date, watchers) together and synchronizes thread title renames if modified.

Verification

• Added comprehensive TDD test suite in tests/test_task_buttons_unification.py (6 tests passing).
• Ran full test suite: 404 passed with 0 failures.
• Ruff linting and formatting passed cleanly.
• Rebuilt Docker application container (docker compose up -d --build app).