fix(extraction): replace fixed traversal stacks with growable arena-allocated stacks

[AhmedHamadto]

Problem

AST traversal functions in the extraction layer use fixed-size TSNode stack[N] arrays. When the DFS stack fills up, the child-push loop exits silently via && top < CAP, dropping entire subtrees without warning.

This affects files with many top-level siblings (e.g., 600 ES imports, 130 Express routes). Reported in #199 — a Node.js routes file with ~130 routes lost data past the 512 cap.

Confirmed: extracting 600 TypeScript imports returns 511 (capped at ES_IMPORT_STACK_CAP = 512).

Fix

Added ts_node_stack.h — a 53-line growable stack backed by the existing arena allocator. Initial capacity matches the previous fixed caps (no extra memory for small files), but doubles on overflow instead of truncating.

Applied to all 14 TSNode fixed stacks across 9 extraction files:

File	Functions fixed	Old cap
extract_calls.c	walk_calls	512
extract_imports.c	walk_es_imports, walk_wolfram_imports	512
extract_semantic.c	walk_throws, walk_readwrites	512
extract_defs.c	extract_elixir_call, walk_variables_iter, push_nested_class_nodes	64–256
extract_usages.c	walk_usages	4096
extract_env_accesses.c	walk_env_accesses	4096
extract_type_refs.c	walk_body_type_refs, walk_type_refs	4096
extract_type_assigns.c	walk_type_assigns	4096
extract_channels.c	scan_string_consts, cbm_extract_channels	4096

Not changed: walk_defs uses walk_defs_frame_t (different struct type), left as-is with its 4096 cap.

Tests

Added test_stack_overflow.c with 7 regression tests:

Test	Before fix	After fix
ts_imports_exceed_512	511/600 FAIL	600/600 PASS
js_calls_exceed_512	600/600	600/600
python_calls_exceed_512	600/600	600/600
go_calls_exceed_1024	1024/1024	1024/1024
express_routes_exceed_512	150/150	150/150
js_deeply_nested_calls	200/200	200/200
yaml_vars_exceed_256	300/300	300/300

Full suite: 2,727 passed, 0 failed.

Design notes

• Arena-backed: old arrays are abandoned in the arena (freed on arena_destroy at end of file extraction). No realloc, no mixed lifetimes.
• Same initial capacity as before — zero extra allocation for files within old caps.
• Net -2 lines (removed 15 #define caps, added growable stack header).
• clang-tidy/cppcheck not available on build machine — CI will validate.

Fixes #199

[DeusData]

Hey, thanks for publishing this PR. I will tackle this immediately after the 15th of April :)