"That file is too large to edit here." and "That could not be changed." live in one module each owner reads #5625

For: Editing a file too large, or a setting or thread change that failed reads the same wherever it is said, on the web and in the terminal, because it is said from one place. Today each sentence below is typed out separately in src/web/pages/browse.ts, src/web/pages/edit.ts, src/web/pages/settings.ts, src/web/pages/thread.ts.

Done:

• [ ] src/web/edit_words.ts exports these sentences (new, or the module that already owns that concept; say which in the pull):

- "That file is too large to edit here." - "That could not be changed."

• [ ] Every file named imports them, and grep -rn for each sentence under src/ finds only the module.
• [ ] Pages, screens and answers are byte-for-byte unchanged: every existing test passes as it is.
• [ ] A new test/web-edit-words.test.ts asserts each file named no longer contains the literal (read as text), and fails if a copy is typed back.
• [ ] Before pushing, run test/web-edit-words.test.ts, the tests of the files you touched, bun x tsc --noEmit and, if src/web changed, bun scripts/design-lint.ts. A red test elsewhere that main also has is named in the pull, not a reason to stop.

Files: src/web/edit_words.ts, src/web/pages/browse.ts, src/web/pages/edit.ts, src/web/pages/settings.ts, src/web/pages/thread.ts, test/web-edit-words.test.ts. Risk: a pure move; change no wording, and touch only the lines the sentences are on.