Adv 2.0 D&D Phase 12 E1c: !expedition start/status/log/abandon

Command surface for the multi-day expedition layer. Wired in
adventure.go alongside !zone. Subcommands: list (delegates to zone
list), start <zone> [Ns] [Md], status, log, abandon, help. Default
outfit is one standard pack; pack tokens parse as e.g. "2s 1d".

start debits coins via p.euro.Debit, refunds on persistence failure,
and blocks if a !zone single-session run is also active. Status
renders the §12.1 daily briefing block with HP, supplies (current
burn factors in harsh conditions / siege), threat threshold label,
and depletion warning if rationing or worse. log shows the last 5
ExpeditionEntry rows. abandon flips status to 'abandoned'.

Start uses the prewritten flavor.ExpeditionStart pool for the
narrative coda and writes it to the log so !expedition log shows it
back. Tests cover parser combinations (1s default, 3s 1d, error
paths), threshold band edges, the start→status→log→abandon roundtrip,
and the underfunded-start no-debit guarantee.

Day cycle (E1d) and !camp (E1e) wire on top in subsequent commits.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/plugin/adventure.go

@@ -250,6 +250,9 @@ func (p *AdventurePlugin) OnMessage(ctx MessageContext) error {
 	if p.IsCommand(ctx.Body, "zone") {
 		return p.handleDnDZoneCmd(ctx, p.GetArgs(ctx.Body, "zone"))
 	}
+	if p.IsCommand(ctx.Body, "expedition") {
+		return p.handleDnDExpeditionCmd(ctx, p.GetArgs(ctx.Body, "expedition"))
+	}
 
 	// 1. Arena commands (work in rooms and DMs)
 	if p.IsCommand(ctx.Body, "bail") {