Release v0.5.2: a hardening release · DABH/localizer

A hardening release from a full review of the runtime, the Action and the Python package. English output is unchanged; catalogs need no migration.

Go runtime

Help texts spanning several lines (Cobra's completion --help, for one) are matched as a whole before line splitting, so they render correctly in every built-in language.
Placeholder captures are checked before they're translated again: prose no longer gets spliced into translations in error output, %w/%v captures are exempt, and a capture that ends a sentence is left alone in help.
Fails open everywhere: a panic in Init, Localize, a help or usage hook or a writer falls back to the original behavior, and a translated template that doesn't parse is never installed.
Commands with their own help or usage function are wrapped too; flag deprecation notices are translated; the completion walk skips DisableFlagParsing commands.
Validation: an unterminated {{, bidi isolates and overrides and other formatting controls, a \r the source doesn't have, or a changed first backquoted span make an entry invalid; 50% off-style space-flag verbs are prose.
The memo cache is bounded (1 MiB, entries up to 1 KiB).
New API: Translate(s, mode) with ModeOutput, ModeHelp, ModeError, and Reset() for tests.
macOS: the preferences plist parser is bounds-checked and only reads regular files up to 8 MiB. catalog.ParseFast matches encoding/json exactly (surrogates, trailing data, duplicate keys).
LOCALIZER_DUMP creates its file exclusively and is ignored for root and setuid processes.

Matching is bounded (no regex backtracking on large outputs), Rich tags are validated as an ordered, balanced sequence, and Typer/Click rendering fails open to the English help.
Multi-line docstring help is translated on Python 3.12 and older; Typer's bundled Click gets translated prompt and confirmation messages; state is restored per render and safe across threads and a second localize().
localize(language="") auto-detects; t() falls back to a pattern translation.
Packaging: a dev dependency group, the built wheel is tested in CI on Python 3.11–3.13 and Typer 0.26; the alias README documents the upgrade from localizer-py.

The Action writes only allowlisted paths (never .git or .github components), adopts only pull requests from the same repository, pushes with the github-token input, and retries its polling.
Third-party actions are pinned by SHA; releases are published only from tags whose commit is on main and whose tests passed.

Precise wording on what is and isn't translated, on human edits and invalid entries, the language lookup order, LOCALIZER_DEBUG, the .localizer.yml validation rules and the service's subprocessors, plus the Action snippets pinned to this release (pull request #18).

The conformance corpus (shared by both runtimes) gained Go-syntax placeholder vectors, round-trip vectors and engine cases with built-in catalogs.