feat(dom): add Playwright selector support, remove nodeId caching

[sfc-gh-mochen]

Motivation

AI agents naturally try to use Playwright-style selectors because they're expressive and precise:

bdg dom click 'button:text("Submit")'

Problem 1: This fails because bdg only supported standard CSS selectors.

AI agents then fall back to bdg dom eval:

bdg dom eval "document.querySelector('button[class*=\"red\"]')"

Problem 2: This fails with "Object reference chain is too long" because DOM elements can't be serialized.

Problem 3: The previous 2-step workflow was clunky:

# Step 1: Query to get indices
bdg dom query "button"
# Found 3 nodes: [0], [1], [2]

# Step 2: Use cached nodeId
bdg dom click 0

This required maintaining a nodeId cache (QueryCacheManager, DomElementResolver) that could go stale.

Solution

With Playwright selectors, one precise selector replaces the 2-step workflow:

# Old way (2 steps + cache)
bdg dom query "button"        # → [0] Save, [1] Cancel
bdg dom click 0               # hope cache is still valid

# New way (1 step, no cache)
bdg dom click 'button:text("Save")'

Changes

New Playwright Selectors

bdg dom query 'button:has-text("Submit")'  # Contains text (case-insensitive)
bdg dom click ':text("Login")'              # Smallest element with text
bdg dom fill 'input:text-is("Email")'       # Exact text match
bdg dom click 'button:visible'              # Only visible elements

Removed NodeId Caching

• Deleted DomElementResolver.ts and QueryCacheManager.ts
• Removed index-based operations (bdg dom click 0)
• Use --index N flag when selector matches multiple: bdg dom click "button" --index 0

Bug Fixes

1. eval serialization: bdg dom eval "document.querySelector('button')" now returns element description instead of failing
2. script execution: Fixed IIFE structure that caused "Uncaught" errors
3. Next steps suggestions: Shows --index examples when multiple matches found

Test plan

• bdg dom query 'button:has-text("Submit")' finds buttons with text
• bdg dom click 'button' --index 0 clicks first match
• bdg dom eval "document.querySelector('button')" returns description
• Multiple matches show correct "Next steps" with --index

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