Addresses snap to runes, not grapheme clusters

sam and acme address runes; pardes snapped #n, line:col, dot and data's
reads to grapheme clusters, so a lone combining mark or a CRLF's \r could
not be addressed. #n, line:col, a search's match, dot (both ways) and data
now land on rune boundaries (modal.runeStart and friends), and the tty's
cell drawing is untouched. The README, fs.md and the skill say so.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 9 insertions, 4 deletions

diff --git a/docs/fs.md b/docs/fs.md
index 8397ed88..e656b66a 100644
--- a/docs/fs.md
+++ b/docs/fs.md
@@ -493,7 +493,7 @@ out of range`.
 takes in `file:12:5`: `12:5` is the point at line 12, column 5, and it
 composes like any simple address (`12:5,14:1`, `12:5+#3`). The column is
 in bytes from 1, as Look's is, clamped to the end of the line and snapped
-back to the start of the character it falls in; a line past the end, or
+back to the start of the rune it falls in; a line past the end, or
 column 0, is `address out of range`. sam would read `12:5` as a syntax
 error.
 Truncating `data` or `xdata` deletes the range `addr` names and nothing
@@ -646,9 +646,14 @@ action's case says where: `x`/`l` a click executed or looked at in the tag
 of the tag. Read `n` bytes of the text, not up to a newline -- bytes here, where acme counts runes. Every offset and
 count pardes serves is in bytes, `#n` and `q0`/`q1` too; the event count
 follows them rather than switch alone, so an acme library reads pardes
-correctly for ASCII text and not beyond it. A `#n` that falls inside a
-character, a multibyte rune or a grapheme cluster, snaps back to where that
-character starts, and `addr` reads back the snapped offset. A click in a
+correctly for ASCII text and not beyond it. Offsets are bytes, but every
+address lands on a rune boundary, as sam's and acme's work in runes, never
+inside a multibyte rune and never widened to a grapheme cluster: a `#n`
+inside a rune snaps back to its start, a `line:col` likewise, a search's
+match covers the runes it touches, and a copy of addr to dot keeps its
+runes, so a lone combining mark or the `\r` of a CRLF is addressable on its
+own; `addr` reads back the snapped offset. (How the terminal draws such a
+text, a cluster to a cell, is apart from this.) A click in a
 tag gives offsets into the whole tag as `tag` reads it, the path first.) An
 open freezes the ring's text the way `/screen` freezes a frame: reads walk it
 and end. Writing `follow` to that same open makes reads past it wait for the