fix: a delimiter inside a quoted field at line start splits the column

[VXNCXNX]

A delimiter inside a double-quoted field is correctly ignored, unless the quoted
field is the first one on the line.

al.csv:

"a,b",xx,y
longer,c,dd

with --column-delimiter=, --column-mode --align:

before:
"a    ,b",xx,y
longer,c ,dd

after:
"a,b" ,xx,y
longer,c ,dd

Align mode makes it visible: the padding is inserted inside the quoted field,
because "a and b" are being treated as two columns. In column mode the cursor
column is the truncated "a rather than the whole field.

Cause

allStringIndex skips a quoted field only after it has already found a
delimiter:

for pos, offSet := strings.Index(s, substr), 0; pos != -1; {
    s = s[pos+width:]
    ...
    if len(s) > 0 && s[0] == '"' {   // only reached after the first match

A quote at position 0 is never examined, so the delimiter inside the first field
is counted.

The fix

Check for a leading quote before the first search, and pull the skip into a
skipQuoted helper so both places do the same thing.

An unclosed quote keeps its current behaviour: strings.Index returns -1 and
s[qpos+2:] becomes s[1:], so only the opening quote is skipped and the rest
of the line is scanned as usual. That matches what the original code did for a
mid-line unclosed quote, and keeps this change to the one bug.

Verification

Two cases in Test_allStringIndex, one for a line that is only a quoted field
and one for a quoted field followed by more columns.

Removing the leading-quote skip fails both:

--- FAIL: Test_allStringIndex/testLeadingDoubleQuoteOnly
    utils_test.go:550: allIndex() = [[2 3]], want []
--- FAIL: Test_allStringIndex/testLeadingDoubleQuote
    utils_test.go:550: allIndex() = [[2 3] [5 6] [7 8]], want [[5 6] [7 8]]

The existing mid-line quoted cases pass under that mutation, which is what pins
the behaviour the change must not alter.

go test ./... is ok across all packages. gofumpt -l is clean on both files I
touched. No new fixture files, so the t.TempDir() and Windows CI hazard does
not arise.

golangci-lint reports 9 issues repo-wide and gofumpt -l flags draw.go and
move_updown.go, all pre-existing on master in files I did not touch.

Disclosure: written with AI assistance (Claude Code). The before and after come from running binaries built from each tree in a real terminal under tmux, and I ran the mutation check myself.

[noborus]

Thank you.
I think supporting fields enclosed in quotation marks is a good idea, but modifying allStringIndex is not advisable.
I believe it would be better to add a separate function.

[VXNCXNX]

Agreed, and there is a better reason than I realised: allStringIndex is also used by the search highlighting, where a quote is just a character.

Pushed a second commit adding allDelimiterIndex, called from allIndex. allStringIndex is now byte-identical to master again.

[noborus]

Thank you for making the changes.

However, regarding the corrections, I would like you to create a separate wrap function instead of modifying allIndex directly. Please update DelimiterRange and maxWidthsDelem in prepare_draw.go to call this new function.

[noborus]

However, regarding the corrections, I would like you to create a separate wrap function instead of modifying allIndex directly. Please update DelimiterRange and maxWidthsDelem in prepare_draw.go to call this new function.

Oh, I'm sorry. Actually, this is fine for now.

[noborus]

I'll go ahead and merge this for now.
Thank you very much.