lint.c: extract the 6 FREESTANDING blocks into a whole-TU-gated lint_host.c (the #741/#812 pattern)

[InauguralPhysicist]

Follow-up to #741, whose builtins.c half landed in #812 — lint.c still carries 6 EIGENSCRIPT_FREESTANDING blocks gating ~950 lines, and they should get the same whole-TU treatment now that src/builtins_host.c establishes the pattern in-tree.

The blocks (current main)

Lines	Size	What
~144–186	41L	g_builtin_name_env + the E003 binding-base machinery
~850–1442	591L	the --api surface index (eigs_api_dump + its lib scan over scandir)
~3164–3591	426L	check_undefined_names (scope-aware name-resolution lint, #404)
~3601–3606	4L	its call-site carve-out
~3726–3804	77L	host arm of the lint file driver
~3827–3941	113L	freestanding arm (dual-implementation eigs_lint_file)

Shape

Unlike the builtins.c case these are not "builtin groups behind a registration seam" — they're lint subsystems plus one dual-arm entry point. The extraction is a lint_host.c (or similar) following builtins_host.c's recipe:

1. Whole TU behind #if !EIGENSCRIPT_FREESTANDING, with the #else arm holding the same linkable stubs the current freestanding arms provide (the ~113L freestanding eigs_lint_file variant moves there).
2. Statics shared between moved and staying code get promoted with a declaration in an internal header — in build: host-only builtins move to one whole-TU-gated builtins_host.c (#741) #812 that was replay_blocks/g_argc/g_argv; here expect the binding-base env and whatever the lint driver shares.
3. TU lists to update (all five, or the link breaks in a different harness than the one you tested): Makefile SOURCES, tools/freestanding_check.sh, tools/freestanding_smoke.sh, tools/embed_stack_soak.sh, web/build.sh.
4. Planted-fault validation in both directions (see build: host-only builtins move to one whole-TU-gated builtins_host.c (#741) #812's Testing section): a host-TU symbol referenced from portable code must fail freestanding_check.sh stage 1 by name; a direct libc call from portable code must still fail by import.

Definition of done

• lint.c's FREESTANDING block count drops to ~0 (dual-behavior carve-outs may legitimately stay, as in builtins.c).
• Full suite release + ASan/UBSan detect_leaks=1 green, leak tally 0.
• Both freestanding_check.sh stages green with allowlist/HAL-roots untouched; freestanding_smoke.sh green.
• Both planted faults demonstrated and reverted.