move loc build tooling to ui-core

[humanapp]

extract loc build tooling into a reusable package

Follow-up refinement to the earlier loc update.
Moves the localization build machinery from microcode-v2
into ui-core as @microbit-apps/ui-core/loc, so that apps built on
this stack get catalog merging, glyph validation, string extraction, and
per-language loc.g.ts/hex generation without reimplementing it.

• loc-tools/ — runLocGen/runCoverageMode API + loc-strings/loc-gen
  bins. Layer discovery walks pxt.json deps (deps-first, app last). App-specific
  steps (tooltip inventory, tagline rule, web snapshots, hex naming) are hooks.
• Generic charset emission — any locale layer may ship locales/charsets.json
  ({lang: {field: string}}); the tool merges, hard-validates (paired lengths,
  no dup code points, glyph coverage), and emits _loc.<field> = "...". The declaring
  library owns each field's meaning.
• Single extractor implementation (deletes the three copies); scripts/locstrings.mjs removed.

[Copilot]

Pull request overview

This pull request extracts localization build tooling into ui-core as a reusable Node-side package (@microbit-apps/ui-core/loc), providing shared layer discovery, catalog merging, glyph/charset validation, and per-language loc.g.ts/hex generation for apps in the microbit-apps stack.

Changes:

• Adds a public @microbit-apps/ui-core/loc API surface and two CLI binaries (loc-strings, loc-gen).
• Introduces orchestration for per-language builds and coverage reporting, including translation-table emission and hex output.
• Adds generic charset resolution/validation/emit support via locales/charsets.json across discovered layers.

Reviewed changes

Copilot reviewed 9 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
package.json	Declares package subpath export for /loc and exposes loc-strings/loc-gen bins.
loc-tools/README.md	Documents the new localization tooling package layout, usage, and configuration.
loc-tools/index.mjs	Exposes the public API entrypoint intended for @microbit-apps/ui-core/loc.
loc-tools/gen.mjs	Implements the per-language build/coverage orchestrator (merge, validate, emit, build, copy hex).
loc-tools/fonts.mjs	Adds font glyph-coverage parsing and a cached coverage provider.
loc-tools/extract.mjs	Refactors source-string extraction into reusable functions + a runLocStrings entrypoint.
loc-tools/emit.mjs	Implements loc.g.ts emission and default-state restore helpers.
loc-tools/charsets.mjs	Implements charset layer resolution and hard validation against font coverage.
loc-tools/catalogs.mjs	Implements dependency-based locales layer discovery and per-language merge.
loc-tools/bin/loc-strings.mjs	Adds CLI wrapper for regenerating locales/<srcLang>.json from sources.
loc-tools/bin/loc-gen.mjs	Adds CLI wrapper for simple consumers to run loc builds/coverage with optional config.

Comments suppressed due to low confidence (1)

loc-tools/extract.mjs:102

• unquote currently only handles \n, \t, and \r escapes. Other valid JS/TS escapes (notably \uXXXX, \xXX, \b, \f, \v, and \u{...}) will be decoded incorrectly, which can corrupt extracted catalog keys/values and make localization builds inconsistent with runtime strings. Consider expanding the escape handling to cover standard JS string escapes.

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