Rename /tmp/claude-diff-* tempfiles to /tmp/code-preview-*

[Cannon07]

Motivation

The plugin was renamed claude-preview.nvim → code-preview.nvim. Everything visible to the user uses code-preview — except the tempfile names used by the core handler:

• ${TMPDIR}/claude-diff-original-<pid>
• ${TMPDIR}/claude-diff-proposed-<pid>
• ${TMPDIR}/claude-patch-input-<pid>.json
• ${TMPDIR}/claude-patch-out-<pid>/

Cosmetic, but inconsistent — a reader poking around /tmp after a hook fires sees claude-* names and wonders if there's a separate claude-specific path.

Scope

• Rename all tempfile prefixes from claude-diff / claude-patch to code-preview-diff / code-preview-patch across bin/core-pre-tool.sh, bin/core-post-tool.sh, and any other shell that references them.
• Update tempfile cleanup globs in core-post-tool.sh to match.
• Worth pairing with a minor version bump in case any user has a stale tempfile from before the rename mid-upgrade.

Out of scope

• Any other rename. The nvim-call.sh tempfile (code-preview-args.XXXXXX) already uses the new convention — leave it.

Acceptance

• No claude-* tempfile references remain in bin/.
• Existing integration tests pass; cleanup globs match new names.