Add buy/sell tools, library docs, and permit/HQ fixes

- tools/buy.py: cash-aware shopping list (construction gap vs empire state's built
  buildings, plus N days of NET operating stock via simulate() so self-produced
  inputs net against consumption), priced at real order-book fill cost, checked
  against cash/reserve, flags multi-trip, binary-searches an affordable size when short
- tools/sell.py: where to post an ask vs hitting the bids now, with expected
  clear time from 30-day traded-volume percentiles
- docs/library.md: module map and patterns for using puga.* directly instead of
  the CLI, plus the "simulate() only knows what the plan lists" gotcha that a
  first version of buy.py hit
- tools/simulate.py: fix --no-hq being a no-op; tools/state.py: permits_total_override
  for when the in-game HQ screen disagrees with FIO's MaximumPermits
- docs/mechanics.md: HQ display vs PRUNplanner's HQ flag, workforce arrival sources
- CLAUDE.md, docs/roadmap.md updated

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/mechanics.md

@@ -58,3 +58,8 @@ Sources: Prosperous Universe dev log #239 "Enlisting Labor" (https://prosperousu
 - Consequences: a habitation building alone (HB2) gets nothing: capacity without a job requiring those workers requests none. The trigger is the production building. Build the housing first (capacity must exist), then the production building: the reserve tops it up at once, up to the instant allowance; the rest arrives at the next weekly report. Buildings run at efficiency = workers present / required until then.
 - Report cadence seen on one planet: weekly, Wednesdays ~08:00 UTC (report #289 on 16 Sep 2026).
 - The old handoff detail "bases keep 75% of workforce between reports" is not in these sources; treat as unverified.
+
+## HQ in game vs PRUNplanner's "HQ" flag (observed 2026-09-21)
+- The HQ screen (level 1, base permits 1 / 2) shows "Efficiency gains: Electronics 20.0%", and 23.3% for the next level (permits 1 / 3). That is exactly the faction bonus formula (Antares electronics 5% x 2 x (3 - 2 x used/total)), so the HQ display is the faction bonus.
+- PRUNplanner's plan flag "HQ" (x1.1 on every building) is NOT visible in live efficiencies (smelters 1.3361, HWP 1.0696 both match the model without it). Keep it off. The HQ upgrade adds a base permit and raises the faction bonus.
+- FIO `/sites` MaximumPermits (3) disagreed with the HQ screen (2). The HQ screen wins; `tools/state.py` supports `permits_total_override`.