Add GWS-powered tasks using fws mock server

[juppytt]

Summary

Add 4 tasks that use gws and gh CLIs against fws (local mock server). Enables realistic Google Workspace and GitHub testing without OAuth.

GWS tasks:

• task_26_gws_email_triage: List unread emails, read them, draft a reply, write a triage report
• task_27_gws_cross_service: Read an email, create a calendar event, share a Drive document
• task_28_gws_task_management: Review task list, read emails for action items, create new tasks

GitHub tasks:

• task_29_gh_issue_triage: List issues/PRs, read them, comment on the most critical, write a triage report

Runner integration auto-starts/stops fws for tasks with category: gws or category: github.

Setup

npm install -g @googleworkspace/cli   # gws CLI
npm install -g @juppytt/fws           # fws mock server
# gh CLI assumed already installed

Changes

• tasks/task_26_gws_email_triage.md - new task
• tasks/task_27_gws_cross_service.md - new task
• tasks/task_28_gws_task_management.md - new task
• tasks/task_29_gh_issue_triage.md - new task
• scripts/lib_fws.py - fws lifecycle management (start/stop/env)
• scripts/lib_agent.py - auto-start fws for gws/github tasks, fix transcript parsing for toolCall/exec format, fix max_completion_tokens for OpenAI judge

Test plan

• Ran task_26 with openai/gpt-5.4-mini, agent used gws CLI correctly
• fws server starts/stops correctly around task execution
• Grading correctly detects gws/gh commands in transcript

Ref: #119