feat(hooks): expose for-the-record and handoff-guard knobs via userConfig

[claylo]

Declare three userConfig keys in plugin.json so users pick the
opinionation level at enable time instead of accepting cnc's baked-in
defaults (or hand-editing hook scripts).
for_the_record_mode block | warn (default: block)
record_subdirs CSV subdirs (default: adrs,decisions,
plans,reviews,specs,
diagrams,superpowers)
handoff_drift_minutes integer minutes (default: 5)
for-the-record.sh now reads CLAUDE_PLUGIN_OPTION_FOR_THE_RECORD_MODE
and CLAUDE_PLUGIN_OPTION_RECORD_SUBDIRS. The subdir list is parsed
into a regex alternation at runtime, so users can replace the default
record-keeping vocabulary with their own. Warn mode allows the write
and attaches a "suggested path" note rather than denying.
handoff-filename-guard.sh replaces the tight "current minute OR
previous minute" string match with a drift window: extract the
YYYY-MM-DD-HHMM prefix, parse to epoch (macOS date -j -f, GNU date -d),
compare abs(diff) against CLAUDE_PLUGIN_OPTION_HANDOFF_DRIFT_MINUTES.
Default 5 min absorbs clock skew and the minute-cusp case while still
catching the "agent hallucinated the hour or day" failures that
motivated the hook in the first place. The separate 30-minute mtime
window for historical edits is untouched.
Defaults match prior behavior, so upgrading changes nothing until a
user sets an option. The spec's date mock was rebuilt around an epoch
anchor so the drift math has a stable "now" to compare against; 46/46
ShellSpec examples remain green.
Release-Note: Configurable for-the-record mode and handoff drift window
Release-Impact: medium