fix(extraction): collapse a damaged C #if group to its first branch before parsing

[danusha2345]

Stacked on #1733 (its commit comes first; rebases to one commit once that lands). Together they close the C extraction extent problem behind #1729: after #1733 a 2,109-file betaflight tree still had 265 C functions the graph filed inside another function; after this, 5.

What the 265 were

Not one cause, and mostly not real functions. 192 of them are literally named if, the rest (NVIC_PRIO_TIMER), (reg), ATMEL_DEVICE_MATCH — phantoms. Verified shape by shape with the shipped tree-sitter-c.wasm:

1. A #if branch that begins with else. tree-sitter-c parses each preprocessor branch as a run of block items, and else cannot start one, so the if (cond) { … } that follows is read as a K&R implicit-int function definition named if, nested in the enclosing function:

   void f(int id) {
       if (id == 1) { a(id); }
   #ifdef USE_V
       else if (id == 2) { b(id); }
   #endif
       else { c(id); }
   }

   (current.c, stm32*_ll_usart.c, _ll_tim.c, _ll_gpio.c, flash_w25n.c, …)
2. A branch that ends with a bare if (…) / else if (…) header whose { body sits after #endif — the STM32H7 ll_utils.c latency tables, 24 phantoms in one file.
3. Branches that leave braces unbalanced (CMSIS arm_mat_*, smartport.c, bus_spi_ll.c): here the enclosing function vanished entirely and its locals leaked to file scope — arm_mat_mult_q15.c had zero function nodes.
4. All-caps block macros in statement position — ATOMIC_BLOCK(NVIC_PRIO_MAX) {, PG_FOREACH(reg) { — which blankCStatementMacroCalls matched in lowercase only.

The fix

blankCUnbalancedConditionalBranches: for a #if … #else/#elif … #endif group where any branch shows one of shapes 1–3, keep the first branch not written #if 0 verbatim and blank every other branch and the group's directive lines (continuations included) to spaces, newlines kept. Balanced groups are untouched; innermost groups first. It runs at the tail of preParseCSource, after restoreDirectiveLines, for the same reason blankCNamedVariadicDefineDots does — it edits directive lines deliberately. blankCStatementMacroCalls also accepts [A-Z_][A-Z0-9_]* now (PascalCase still excluded, for the C++-constructor reason in its comment). The C++ grammar parses both snippets cleanly, so the C++ path is left alone; the pre-parse precedes the kernel route point, so the kernel needs no change.

Measured

betaflight fork, 2,109 .c files, wasm arm:

	#1733	this
C functions nested inside another C function	265	5
C function nodes	39,993	39,772 (260 phantoms gone, ~39 real functions back)
fuzzy calls	154	37

Edge-set delta against the #1733 index, rows keyed with resolvedBy: 1,263 lost / 729 gained. Lost: 709 exact-match calls whose source was a phantom (if@…) or a file node holding leaked locals, 490 file-level contains for those locals (pInA, row, flag), 53 references, 11 function-refs. Gained: 671 exact-match calls from the recovered functions (USBD_LL_Init → HAL_PCD_Init, LL_TIM_DeInit → …, processSmartPortTelemetry → erpmToRpm) and 43 contains for them. Functions that now exist with their real extents: spiInternalInitStream/StartDMA/StopDMA (bus_spi_ll.c), processSmartPortTelemetry (522–903), esc4wayProcess (429–929), arm_mat_mult_q15. Ten lost and ten gained rows read against source: every lost row is a re-attribution from a phantom or a file node, not a real call gone.

The 5 that remain: four if SILABS_DEVICE_MATCH { / else if ATMEL_DEVICE_MATCH { in serial_4way.c (a paren-less macro as an if condition) and one STATIC_DMA_DATA_AUTO union { … } testBuffer; in flashfs.c — each its own narrow blank, not folded in here.

Tests

extraction.test.ts: a unit test of the blank (length and line count preserved, a continuation line blanked, the first branch kept, the second branch and the directives blanked, a balanced #ifdef untouched, #if 0 keeps the live branch, identity on a file without groups) and an end-to-end index where a function after a damaged group used to be a phantom (NVIC_PRIO_MAX) and now has its own extent and top-level name; the end-to-end test fails without the change. extraction.test.ts + resolution.test.ts: 815, tsc clean.

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