fix: make DWARF line lookup and cross-CU indexing precise#173
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Store every DWARF line row for a PC instead of replacing earlier rows in the address-to-line map. Optimized binaries can legitimately emit multiple rows for one instruction, such as inline or header locations sharing a PC, and source-line queries need to score all of those candidates. Keep generic nearest-line and prologue lookup behavior compatible with the old representative row semantics, while teaching source-line queries to prefer the requested file and line when exact-PC duplicates exist. Add a dwarf_index_regressions e2e case that finds a real same-PC line-row fixture in complex_types_program and verifies both address lookup and best-effort source-line query preserve the requested line.
DWARF line rows cover half-open address ranges. Preserve duplicate rows while recording the next row address so nearest-previous source lookups do not cross end_sequence boundaries or gaps. When choosing source-line probe addresses, only treat an address as a statement row if the matching row belongs to the requested file and line. This avoids selecting unrelated same-PC inline/header rows. Add unit and e2e coverage for same-PC statement filtering, zero-length rows, and sequence gaps. Also update an existing e2e assertion to satisfy inline format linting.
Follow origin/specification refs that point outside the current CU when building the lightweight index, using absolute .debug_info offsets for caches and recursion guards. Add unit and object-backed e2e coverage for cross-CU origin/spec names, and tighten source-line hint path matching so duplicate-PC rows cannot reintroduce unrelated same-basename files.
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This PR fixes a set of DWARF lightweight-index and source-line lookup regressions around duplicate line rows, line-sequence boundaries, and cross-CU origin/specification references.