refactor(vocabulary): the retired engine's name reaches zero outside docs/adr (47 -> 0)

[ywatanabe1989]

Ruling

Operator, 2026-08-31:

「スクライトなど我々には関係ないので、adr以外許さない」 - the retired storage engine is irrelevant to us; nothing outside ADRs is permitted.
「テストもいらない、スクライトとか眼中にもない、そんなテストはいらない」 - the guard tests for it are not wanted either.

Scope

src/ was measured first and is clean - zero hits. This is therefore a docs / tests / examples vocabulary pass only; no live code was touched.

	outside docs/adr
before	47 matching lines across 18 files
after	0

Deleted - subject is the retired engine itself

• .scitex/clew/runtime/db.sqlite - a 69 KB binary database committed into the repo. An artifact of the retired engine, not source.
• examples/_legacy/scitex/db/_sqlite3/ - 12 example stubs, every one of them zero bytes. Their names carried the word; their contents carried nothing.
• examples/_legacy/notebooks/19_scitex_db.ipynb - a legacy tutorial whose subject is the retired engine's API (19 of the 47 hits lived here). The master-index entry pointing at it was removed with it, so no link dangles.

Reworded - real history and live docs, kept readable and true

• README.md, docs/05_ADDITIONAL_MODULES.md - the scitex.db section now documents the PostgreSQL client. stx.db.PostgreSQL(dbname=...) is the real signature, verified against the installed package, so the example still runs.
• docs/sphinx/core_concepts.rst, docs/sphinx/modules/io.rst - clew provenance now reads "a local database". The mechanism described is unchanged.
• docs/guides/CROSSREF_API_CONFIGURATION.md - "single-file local database with indexed fields".
• .env.d.examples/, a pyproject.toml comment, two .gitignore files, the legacy io guideline table, and the schematic example's figure label.

Tests - nothing weakened, skipped or xfailed

• test_cross_package_imports.py - dropped "scitex_io._load_modules._sqlite3". That module no longer exists (find_spec -> None), so this auto-generated snapshot entry was permanently hitting the file's own pytest.skip path. Removing a dead entry costs no coverage.
• test_integration.py - test_db_delegates keeps its stated subject. Delegation to scitex-db is still proven by the PostgreSQL and check_health asserts; only the retired engine's probe is gone.
• scripts/maintenance/_pypi_packages.py - the stdlib-inventory entry is provably dead here: sync_pyproject_extras.py scans <repo>/src, and src/ has zero references, so the entry can never be consulted.

Verification, with positive controls

An empty grep from a broken pattern looks identical to a real absence, so the search itself was proved to run.

check	result
after - working tree, outside docs/adr	ZERO (exit 1)
after - staged index, outside docs/adr	ZERO (exit 1)
after - whole tree including docs/adr	ZERO
tracked filenames containing the word	ZERO
CONTROL - same pattern + pathspec vs origin/develop	finds 18 files -> the search is not broken
CONTROL - same live-tree search for postgres	finds 6 files -> the working-tree search really runs

Note on the usual control. This repo's docs/adr/ holds a single ADR (0001-relocate-media-to-scitex-etc.md) that never mentions the engine, so the standard "docs/adr must still show hits" control is not available here. The two controls above stand in its place.

Suite: 315 collected in the integration tests, 0 collection errors. The two edited files run 181 passed, 52 skipped, 1 xfailed, 0 failed.