i18n: add Polish (pl) interface language

Complete Polish catalog (4,492 rows): every menu string, tl! literal,
plural and status/error message, enforced by the existing completeness
tests (complete_menus, KEEPS_MENU_NAMES, COMPLETE_MESSAGES).

- pl.tsv: clean-room translation from the English meaning, following
  common Polish desktop-software conventions (obszar kompozycji for
  artboard, obszar roboczy for workspace, obrys, wypełnienie, próbki…)
- plural_polish: one / few (2–4, not 12–14) / many (0, 5–21, 25…)
- every pl-* locale (pl-PL, pl_PL.UTF-8) resolves to it
- tests: Polish plural forms, vocabulary, nested message translation;
  Polish letters in the bundled-font coverage test
- docs: README, development.md, localization-parity.md

Drafted with AI assistance; native review welcome.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DukHNvUY45rjRnvtz91x33

docs/development.md

@@ -178,7 +178,8 @@ complete; `fr-FR`, `fr-BE`, `fr-CA`, `fr-CH` and every other `fr-*` locale resol
 complete; `it-IT`, `it-CH` and every other `it-*` locale resolve to it), Russian (`ru`, complete; every `ru-*`
 locale such as `ru-RU`, `ru-BY` or `ru-KZ` resolves to it), Ukrainian (`uk`, complete; `uk-UA`,
 `uk_UA.UTF-8` and every other `uk-*` locale resolve to it; integer plurals use one/few/many), Hungarian (`hu`, complete;
-`hu-HU` and every other `hu-*` locale resolve to it; a count takes the singular, so plurals have one form), Czech (`cs`, every menu label) and Brazilian Portuguese
+`hu-HU` and every other `hu-*` locale resolve to it; a count takes the singular, so plurals have one form), Polish (`pl`, complete; `pl-PL` and every other `pl-*`
+locale resolve to it; plurals use one/few/many, with 21, 31 … taking many), Czech (`cs`, every menu label) and Brazilian Portuguese
 (`pt-br`, every menu label and every `tl!` literal). Untranslated text falls back to English until its rows are added.
 
 - `tl!("…")` translates a literal into the language the UI is drawn in; `i18n::t(s)` is the same for a
@@ -206,7 +207,7 @@ locale such as `ru-RU`, `ru-BY` or `ru-KZ` resolves to it), Ukrainian (`uk`, com
   control channel, MCP and tests read them) and are translated only where the status bar draws them
   (`i18n::msg`). `@msg` catalog rows hold a whole message or a template such as
   `Couldn't open {name}: {e}`; `{_1}`, `{_2}` … stand for the format string's `{}`, and the values in the
-  placeholders are translated in turn (the reason after `: {e}` is often a message too). Czech, German, Spanish, French, Hungarian, Italian, Japanese, Korean, Russian, Ukrainian and Vietnamese cover every
+  placeholders are translated in turn (the reason after `: {e}` is often a message too). Czech, German, Spanish, French, Hungarian, Italian, Japanese, Korean, Polish, Russian, Ukrainian and Vietnamese cover every
   message literal the test scan finds (`complete_languages_translate_every_message`, languages listed in
   `COMPLETE_MESSAGES`): a new `Err("…")`, `Other(…)`, `#[error(…)]` or `status(…)` message needs a row in each of those catalogs (`VECTORCRAFT_I18N_DUMP_MESSAGES=messages.txt cargo test -p vectorcraft-ui-egui
   complete_languages_translate_every_message` lists them all). Other languages show messages in English

docs/localization-parity.md

@@ -50,9 +50,10 @@ plus review. Native-speaker review is human work and isn't in the hours.
 | Russian | `ru` | 4,009 / 4,020 | full |
 | Ukrainian | `uk` | 4,009 / 4,020 (one/few/many plurals) | full |
 | Hungarian | `hu` | 4,524 rows: menus, `tl!` literals and messages complete (tests); one plural form | full |
+| Polish | `pl` | 4,492 rows: menus, `tl!` literals and messages complete (tests); one/few/many plurals | full; native review pending |
 | Czech | `cs` | 4,411 catalog entries, including 636 `@msg` rows (measured locally 2026-10-11); menu, literal and message coverage enforced by tests | catalog complete; render-site gaps reduced; native review pending |
 
-Fourteen non-English catalogs in all. Illustrator, as its public documentation lists, ships around two dozen
+Fifteen non-English catalogs in all. Illustrator, as its public documentation lists, ships around two dozen
 interface languages (including Polish, Dutch, Turkish, the Nordic languages, Hungarian, and Middle East
 editions with Arabic and Hebrew); it doesn't ship Hindi, Indonesian or Vietnamese.
 
@@ -83,6 +84,7 @@ font for the web build.
 | 2026-10-13 | minor | Czech: 128 more strings translated (tool names, PDF and Image Trace presets, pie graph options and others added since the catalog was completed; #1461); the entry count in the table is the 2026-10-11 measurement; native review still pending; scores and estimates unchanged |
 )
 | 2026-10-12 | minor | Korean (`ko`) catalog added, complete under the tests (menus, literals, messages); 12-language score 54% → 63%, hours 70–110 → 60–100 |
+| 2026-10-12 | minor | Polish (`pl`) catalog added, complete under the tests (menus, literals, messages; one/few/many plurals) |
 | 2026-10-12 | minor | Hungarian (`hu`) catalog added, complete under the tests |
 | 2026-10-11 | minor | Czech render-site follow-up: file-dialog filters, diagnostics, preset numbering, contributor tooltips/plurals, gradient grammar and contextual printer mark styles; estimates unchanged |
 | 2026-10-10 | major | First per-language table, measured from the catalog row counts against the complete French catalog |