Data Model: Retire mission_read_path Backcompat Shim

No domain data entities. This is a code-retirement / architectural-debt mission; it introduces no persisted data, schemas, or value objects.

The only structured artifacts touched are architectural-gate ledgers, recorded here for precision:

Architectural ledger entries (state being removed)

ArtifactKey / memberBeforeAfter
tests/architectural/_baselines.yamlcategory_4_backcompat_shims98
tests/architectural/test_no_dead_modules.py_CATEGORY_4_BACKCOMPAT_SHIMS"specify_cli.mission_read_path"presentremoved
tests/architectural/test_no_dead_symbols.py_CATEGORY_C_BACKCOMPAT_SHIM_REEXPORT"specify_cli.mission_read_path::resolve_mission_read_path"presentremoved

Invariant (C-001): _baselines.yaml.category_4_backcompat_shims MUST equal the live size of _CATEGORY_4_BACKCOMPAT_SHIMS after the edit. test_ratchet_baselines.py enforces this equality and additionally forbids the value from increasing relative to the committed baseline (SHRINK ratchet). Decrement (9→8) satisfies both.

Symbol contract (unchanged)

SymbolCanonical homeVisibilityImporter after repoint
_resolve_mission_read_pathspecify_cli.missions._read_path_resolverprivate (not in __all__)imported + aliased to resolve_mission_read_path in test_coord_reader_fixes.py
StatusReadPathNotFoundspecify_cli.missions._read_path_resolverpublic (__all__)imported directly

No symbol is added, renamed, or promoted; only the shim's redundant re-export is removed.