v0.15.3

Parser stability and harness release.

Added

• C/C++ lexer bridge now accepts #embed directive lines and
  __has_embed(...) conditional feature-test forms (including parameter
  variants) without parse errors.
• Scoped Canopy harness runner under cgo_harness/docker/. The wrapper mounts
  the host Canopy binary into the Docker harness, applies memory/CPU/PID caps,
  uses a host-side timeout watchdog, and scopes analysis to one package with
  generated blobs/worktrees excluded by default.

Changed

• ts2go batch execution is parallelized, reducing generated-grammar
  conversion wall time on multi-core machines.
• External scanner adaptation now tolerates source/target external-symbol count
  mismatches. AdaptExternalScannerByExternalOrder can match shared symbols by
  name, leave unpaired target symbols disabled, and size the source-valid bitmap
  to the source scanner rather than assuming equal external lists.
• Moved cgo harness sample/profile fixtures under testdata directories and
  updated the harness docs and scripts to use the new paths.
• GLR stack culling now shares the keyed retention path across full and
  incremental parses while preserving the previous incremental tie-breaks.
• Parser-result compatibility dispatch is now separated from core tree
  assembly, with mixed compatibility shims split into language-owned files and
  shared node helpers moved out of language-specific modules.
• Parser tests are split by responsibility, public parser-result regression
  tests live under parser_result_test, and larger parser-result Python source
  fixtures now live under testdata/parser_result.

Removed

• Dropped unused query matcher rollback compatibility wrappers now that
  predicate-aware matching is the only call path.
• Removed unused internal parser, reduce, incremental, and parser-result helpers
  left behind by recent recovery and normalization rewrites.
• Removed stale internal planning/spec docs from the OSS tree.
• Removed unused private grammar and grammargen helper code found by the
  maintenance sweep.
• Moved ad-hoc grammargen diagnostic tests behind an explicit build tag and
  removed the print-only disassembly lexer probe from the normal test suite.
• Removed the duplicate legacy GLR stack-retention selector from parser
  internals.

Fixed

• Re-landed the arena-retention and repo-cleanup fixes from the recovered
  main-line commits after the accidental reset.

Performance

• JavaScript and TypeScript full parses cap merge survivors per key at 4. Large
  JS bundles can otherwise keep too many near-equivalent GLR branches alive and
  spend most parse time in merge-equivalence checks. Incremental parsing and TSX
  keep their existing budgets.
• Markdown and markdown_inline full parses use tighter initial GLR stacks and a
  higher markdown-specific node budget. Dense inline-heavy markdown now prunes
  early without forcing repeated node-limit retries on normal documents.