feat: add cwd and args info to snapshot headers

[branchseer]

Why

Snapshot files currently only show source, expression, and input_file in the YAML header. To understand what a snapshot is testing, you have to cross-reference snapshots.toml. Adding cwd and args to the header makes each snapshot self-describing, making human review easier.

Summary

• Add info field to plan snapshot headers with args (array) and optional cwd
• Add info field to E2E snapshot headers with cwd when non-default
• Makes snapshots self-describing without cross-referencing snapshots.toml

Test plan

• cargo test -p vite_task_plan --test plan_snapshots passes
• cargo test -p vite_task_bin --test e2e_snapshots passes
• Verified headers in generated .snap files contain correct info

🤖 Generated with Claude Code

[branchseer]

• feat: add cwd and args info to snapshot headers #175 👈 (View in Graphite)
• main

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