fix(extract): guard against large SQL file stack overflow (#691)

[lg320531124]

Summary

The tree-sitter SQL grammar (39 MB parser.c) uses deeply recursive non-terminals that overflow the C stack on files with many statements (e.g. schema dumps >10K lines, stored procedures). The stack overflow kills the thread before any timeout callback can fire, so a pre-parse guard is the only safe mitigation.

Changes

• Add a line-count guard (CBM_SQL_MAX_LINES = 5000) in cbm_extract_file() that returns has_error for SQL files exceeding the threshold
• The pipeline skips the file gracefully instead of crashing

Why line-count, not byte-size?

• tree-sitter's recursive descent parser pushes a stack frame per statement
• A 500KB SQL dump with 10K CREATE TABLE lines overflows the default 512KB macOS thread stack
• A 2MB compressed binary blob with few newlines does NOT overflow
• Line count is the correct proxy for SQL stack depth

Why 5000 lines?

• Default macOS thread stack: 512 KB
• tree-sitter SQL frame size: ~100 bytes per recursion
• 5000 lines → ~500 KB stack usage (safe margin)
• Captures virtually all crash-inducing workloads

Why in cbm_extract_file(), not the discover layer?

• The discover layer only checks byte size and knows nothing about SQL
• The guard must be where tree-sitter is invoked — that is where the crash happens
• Keeps the change minimal and colocated with the dangerous call

Testing

• All 5720 existing tests pass
• Small SQL files (<5000 lines) parse normally
• Large SQL files (6000 lines) are skipped gracefully with has_error=true

Fixes #691

Related: #668 (original report)

[DeusData]

Huge thanks for opening this PR and for the work you put into it.

The maintainer shop is currently full, so this may sit for a bit before it gets a proper review. We will come back to this as soon as possible with real feedback; I wanted to make sure it did not sit unacknowledged in the meantime.