feat: enable playwright artifacts and screenshot protocol

[fg-nava]

Ticket

Resolves: Enable Playwright artifact storage across environments

Changes

• Artifacts to filesystem/GCS
  • Output dir for Playwright MCP artifacts: artifacts/ enabled via --output-dir
  • Added --save-session and --save-trace for full artifact storing
  • File: src/mastra/mcp.ts
• Screenshots
  • Added the “Screenshot Protocol” instructions to system prompt
  • Take one full-page (fullPage: true) screenshot after completing each benefits application page, not per interaction
  • Example tool call is also set in the prompt since gemini-2.5-pro isn't so great at following instructions (sonnet is much better).
  • File: src/mastra/agents/web-automation-agent.ts

Context for reviewers

We need consistent, reviewable browser automation output (screenshots, traces, sessions)

Artifact Storage Locations

.mastra/output/artifacts/
├── page-{ISO-timestamp}.png                    # Screenshots (auto-generated timestamps)
├── session-{timestamp}/                        # Session artifacts (--save-session)
│   ├── session.md                             # Session summary and metadata
│   └── {number}.snapshot.yml                  # DOM snapshots at different points
└── traces-{timestamp}/                         # Playwright traces (--save-trace)
    ├── trace.trace                            # Main trace file for Playwright inspector
    ├── trace.network                          # Network activity logs
    └── resources/                             # Additional trace resources

[KayTV]

Can you update the PR with the description of what you changed?

[KayTV]

LGTM

[KayTV]

I think a note I have is not taking screenshots of security risk ones like SSN. Most forms will hide this after they enter in their SSN with *** but there are less technical advance forms that do not have this feature

[fg-nava]

Good point. I agree, the defensible approach is to not take a screenshot. However if the form is a single page this means we are not able to visually confirm.

There are targeted approaches to taking screenshots as well:

https://playwright.dev/docs/screenshots#element-screenshot

[fg-nava]

Leaving as is for now based on standup conversation, but underscoring this as a security consideration along with other artifacts (traces, snapshots).