docs(adk): audit Handling longform logic, conversations, and setup sections

Continues the audit pass. Fixed inaccuracies, documented missing
features, tightened prose, inlined dev console mentions, and refreshed
screenshots.

Workflows:
- Added state prop, workflow.fail, workflow.execute
- Added step.progress, noted getOrCreate default statuses
- Rewrote ambiguous step-name uniqueness paragraph
- Updated request.workflow.provide examples to pass request.step
- Inlined workflow dev console mention into Create section

Conversations:
- Fixed tools title casing (Define Tools -> Define tools)
- Clarified customComponent vs custom message types
- Added execute() signal? prop (AbortSignal cancellation)
- Noted nudge.interval default and max-unlimited behavior
- Replaced Chat page screenshot with agent-steps screenshots
- Fixed webchat integration install note (no auto-prompt)
- Replaced duplicated Traces blurb with link to debugging page

Setup:
- Fixed swapped default model claim in configuration
- Fixed evals.idleTimeout unit (seconds -> milliseconds)
- Title casing: Agent Configuration / Environment Setup -> sentence case
- Removed evals row pointing at src/evals, updated to evals/
- Trimmed project structure table to core files only
- Reworked integrations install vs configure framing
- Enable/disable example now leads with string shorthand
- Inlined secrets and config dev console mentions into existing sections

Screenshots refreshed: workflows, environment selector, secrets,
config variables, integrations hub, integration config.

Removed trailing next-page Cards from every page in these sections.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jacksonyzj