Update iso-codes to v4.20.1 and prepare 2026.9.2

[Atem18]

Packaging

• Declare the licence as a single SPDX expression. The metadata claimed both LGPL-2.1 and MIT, which some licence scanners reject. The bundled data comes from Debian's iso-codes, so LGPL-2.1-or-later is the correct one.
• Stop shipping the catalogues a second time under the obsolete filenames that upstream installs as symlinks. A wheel materialises those into full copies, which was doubling the package: 15 MB down to 8.1 MB, all 163 languages kept. The old domain names still resolve through translate() and translator().
• Add a [build-system] section and set include-package-data = false, so the configured package-data globs are actually honoured.
• Require Python 3.11, and support 3.14 including the free-threaded build.

Data

• Rewrite update.sh for meson. Upstream dropped autotools in 4.19.0, so the previous ./configure && make could no longer build it.
• Refresh to v4.20.1. Six currencies were withdrawn upstream (BGN, HRK, ANG, CUC, SLL, ZWL) and three added (XCG, ZWG, XAD); Bulgaria and Croatia now use the euro.

Library

• find() requires every keyword to match. It previously returned on the first indexed field and ignored the rest, so find(alpha_2="US", name="Nonsense") returned the United States.
• search() ignores word order and ranks its results. ISO stores many names inverted, so search(name="Republic of Korea") returned nothing.
• Add search_fuzzy() for queries containing typos. search() is unchanged and never guesses: the approximate pass runs only when an ordinary search finds nothing.
• Add translate(), translator() and available_languages(), replacing the raw gettext recipe in the README.
• Load the datasets on first use instead of at import, and drop the duplicate storage in ISONamespaceRecord. Import falls from ~145 ms to ~29 ms, and get() is around 180x faster.

CLI

• Fix --format json and --format csv printing "No results found." when there were no matches, which is neither valid JSON nor valid CSV.
• Fix --fields being ignored by --format json.
• Add "isocodes locales" to list the bundled translations and remove unwanted ones. It previews by default and needs --yes to delete anything.
• Add --fuzzy.
• Collapse the six near-identical search handlers and their parsers into one table-driven implementation, and remove branches that could not be reached. The command line interface is unchanged apart from --fuzzy.

Tests and CI

• 273 tests, up from 136, at 100% coverage enforced by fail_under.
• Add a coverage workflow, run the test workflow on pushes to main, and configure codespell so pre-commit can pass on the vendored data.