vms-9f6: real LIB$TABLE_PARSE / LIB$TPARSE TPARSE engine (RTL prereq for MMK + vms-486)

[baron-3dl]

vms-9f6 -- replace the lib_tparse.c stub with a real TPARSE engine

Parent: vms-801 (source-compat / RTL coverage). Unblocks the P2 gap in the
self-host MMK spine (docs/design-self-host-mmk-spine.md 1.3): lib$table_parse
was absent and lib$tparse was a 14-line SS$_UNSUPPORTED stub. This blocks
parse_tables.mar -> C (vms-486) and native MMK.

What changed

• src/libvms/rtl/lib_tparse.c -- real TPARSE finite-state engine. Ordered
  per-state transitions matching literal chars, case-blind keywords (optional
  TPA$M_ABBREV), the TPA$_ special classes (LAMBDA/EOS/ANY/BLANK/ALPHA/DIGIT/
  SYMBOL/STRING/DECIMAL/OCTAL/HEX/UIC), and subexpression calls; token/number
  capture into the TPA block; action-routine callbacks that get the block address
  and whose even (failure) return rejects the transition and backtracks (MMK's
  CHECK_GNU/CHECK_COND gate pattern); TPA$M_BLANKS inter-token blank skipping;
  TPA$_EXIT/TPA$_FAIL/next-state dispatch. Exports both lib$table_parse
  and the lib$tparse alias.
• src/libvms/include/tpadef.h -- OVMX C table format (TPA_GRAMMAR/TPA_STATE/
  TPA_TRAN, action typedef). The state/key table byte layout is unpublished by
  VSI, so this is labelled an OVMX design choice per Rule 8. It is the format
  vms-486 will target; observable behaviour, not table bytes, is what matches VMS.
• src/libvms/include/lib$routines.h -- declare lib$table_parse.
• src/libvms/CMakeLists.txt + src/vmslink/mk_libvms_shr.sh -- add
  rtl/lib_tparse (the shr vector is nm-generated, so both names auto-export).

Clean-room (Rule 8)

Semantics derived only from the public VSI OpenVMS RTL Library Reference
(LIB$TABLE_PARSE / LIB$TPARSE, the TPA$ token classes, the action-routine TPA
block). No VSI/HPE source or binaries consulted.

Tests

• tests/libvms/test_lib_tparse.c -- five real grammars (UIC parser, a
  SET/SHOW command language, action-driven backtracking, a subexpression, keyword
  abbreviation) driven through lib$table_parse, asserting status + action side
  effects. 23 assertions, all pass.
• Full Debug ctest: 100% (156 tests, 0 failed) (11 e2e Skipped, pre-existing).
• Native-link reproduced locally (OVMX_LINK_NATIVE, x86_64 link_native_graph):
  9 artifacts, all EM_X86_64, zero DT_NEEDED; LIBVMS$SHR.EXE .vms$sv now carries
  lib$table_parse + lib$tparse.

Not merged; work item not closed here.

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