docs: "always decodeURIComponent(currentFilename)" pitfall doesn't account for filenames containing a literal `%`

[carochacs]

CLAUDE.md's Common Pitfalls section says:

currentFilename may be percent-encoded — always decodeURIComponent(currentFilename) before building URLs in pane plugins.

"May be" + "always decode" is a lossy pair. If currentFilename is sometimes not encoded, and a real filename legitimately contains a % (e.g. 100% Live.sloppak), an unconditional decodeURIComponent call either throws a URIError (malformed sequence) or silently corrupts the name (a %XX that happens to look like valid encoding). The doc doesn't establish the invariant it's assuming ("currentFilename is always exactly-once encoded when this rule applies").

Suggest one of:

• Establish and document the actual invariant at the source (playSong always receives an encoded name / always receives raw — pick one and enforce it), or
• Decode defensively: try { decodeURIComponent(x) } catch { x }, or detect whether the string is already encoded before decoding.

[pullfrog]

  ^{｜ Build this ➔ ｜ Make a plan ➔}