fix(pipeline): escape dynamic edge properties as JSON

[tmonestudio]

What does this PR do?

Prevents malformed JSON in edge properties when extracted values contain quotes, CR/LF, or other control characters.

Two edge builders serialized parser-derived strings directly:

• sequential import edges wrote local_name without escaping;
• parallel GraphQL edges escaped the callee but not the operation text.

A multiline Rust import alias or GraphQL operation could therefore make json_valid(properties)=0, and JSON-backed SQLite checks/queries could fail with malformed JSON.

Fix

Use the existing cbm_json_escape helper for both dynamic values before formatting the properties object.

The regression fixture uses a multiline GraphQL operation and asserts that every emitted edge property remains valid JSON.

Validation

• Windows production build succeeds with GCC.
• MCP suite: 145 passed, 6 platform-specific skips.
• Independently validated with PRAGMA quick_check and json_valid after reindexing affected repositories.

Checklist

• Every commit is signed off (git commit -s)
• Full make -f Makefile.cbm test (left to CI; local Windows sanitizer runtime is unavailable)
• Full lint (left to CI)
• New behavior is covered by a reproduce-first regression fixture