LLE utf8: one ANSI-aware width for LLE, not three

[berrym]

Third slice of duplicate-path item 6 — the LLE half.

Three walks, three answers

site	what it did
completion_menu_renderer	correct: ECMA-48 final byte + the width table
completion_menu_state	one column per byte — a CJK menu entry measured 3 instead of 2, so the menu laid out too wide
prompt composer	ended a sequence only on m — \033[K or a cursor movement left the rest of the prompt measuring zero

The correct one is promoted to lle_utf8_visible_width, beside the lle_utf8_string_width primitive it builds on. The other two become calls. No escape walk remains in any of the three files.

Why two canonical functions, not one

Display got the same consolidation in #755/#756. These two layers deliberately keep one implementation each rather than sharing: display depends on LLE and not the reverse, so a single shared function would either live in LLE and be reached across the seam by display, or live in display and invert the dependency.

Two canonical answers — one per layer — is the correct outcome under that constraint. It is also six fewer than there were this morning.

Verification

tests/lle/unit/test_char_width.c covers the shared function on exactly the terminators that broke the individual copies — cursor hide/show (l, h), erase-line K, and \033[3~ whose final byte is not a letter — plus width from the table rather than a byte count: a wide character inside escapes, an em dash (one column, which the composer's guess made two), and a base plus combining mark.

Full suite 197/197. ASan 65/65. Net −128 lines across the three files.

One note on the test: it derives every length with strlen. An earlier version hand-counted one and passed a length two bytes past the end of the literal, reading whatever followed — and the failure looked exactly like a width bug in the code rather than in the test.

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/lle/unicode/utf8_support.c	89.47%	2 Missing ⚠️

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