fix(expansion): `${@/#/prefix}` and `${@/%/suffix}` do not apply to positional params

[chaliy]

Summary

Pattern substitution on `$@` (all positional parameters) with `#` (prefix) or `%` (suffix) anchors does not modify the values.

Reproduction

set -- "hello" "world" "test"
prefix="tag_"
set -- "${@/#/$prefix}"
echo "$@"
# Expected: tag_hello tag_world tag_test
# Actual: hello world test (unchanged)

set -- "hello" "world"
set -- "${@/%/.html}"
echo "$@"
# Expected: hello.html world.html
# Actual: hello world (unchanged)

Real bash comparison

$ bash -c 'set -- "hello" "world"; p="tag_"; set -- "${@/#/$p}"; echo "$@"'
tag_hello tag_world

Context

Bashblog uses this in `posts_with_tags()` to construct tag file paths from tag names:

posts_with_tags() {
    (($# < 1)) && return
    set -- "${@/#/$prefix_tags}"   # prepend "tag_" to each arg
    set -- "${@/%/.html}"          # append ".html" to each arg
    sed -n '...' "$@"
}

Without this, the function passes raw tag names as filenames instead of `tag_NAME.html`, breaking tag page lookups.

Expected behavior

`${@/#/string}` should prepend `string` to each positional parameter. `${@/%/string}` should append `string` to each positional parameter. Same for `${array[@]/#/}` and `${array[@]/%/}`.