fix(buyer): stop skip-starvation, add cap headroom, escalate own bids to buyout

[icemansparks]

Problem

Player auctions were never bought or only cycles later (#28). Verified live: the 5 lowest-ID player auctions were permanently above the bot's buy cap, and because skips consumed the 5-bids-per-15-min budget and the candidate set was scanned lowest-ID-first, buyable auctions further down the queue (e.g. Runed Copper Bracers at 21090 vs cap 21709) were never even evaluated. Two auctions the bot had bid on were frozen until expiry by the buyguid exclusion.

Changes (all in Buy())

1. Starvation fix - candidates go into a shuffled vector instead of an ID-ordered set; skipped auctions no longer consume the BidsPerInterval budget, only successful bids/buyouts do. Each candidate is evaluated at most once per run.
2. Cap headroom - when a price override exists, the max-buy cap gets at least 15% headroom above avgPrice. 64% of override rows currently have minPrice == avgPrice, which collapsed avg + (avg - min) to exactly avg while the seller lists at avg +-10%.
3. Buyout escalation - the query no longer excludes auctions the bot already leads. It never re-bids (would outbid itself); it escalates to a buyout when the buyout still fits the cap, so sellers get paid promptly instead of waiting for expiry.

Notes

• With multiple bot GUIDs configured, one bot char can buy out an auction another bot char leads (the previous bidder is refunded by mail). Single-GUID setups (like ours) are unaffected.
• Worst case per run is now one pass over all non-bot-owned auctions instead of BidsPerInterval set pops; that's tens of rows on a bot-populated AH.

Verification

• AuctionHouseBot.cpp.o compiles clean on testcore (GCC 12, -Werror).
• Self-review pass: no blockers; opsDone increments exactly once per DB-writing operation, no self-outbid path, includes already present.

Closes #28

[Copilot]

Pull request overview

This PR fixes buyer-side auction evaluation starvation and improves purchase behavior so player listings that are within cap are actually considered and bought promptly, addressing issue #28.

Changes:

• Randomizes candidate auction evaluation order and ensures each candidate is evaluated at most once per run.
• Makes skipped auctions not consume the per-interval bid/buyout budget (only successful bid/buyout operations increment the budget counter).
• Keeps auctions the bot already leads in the candidate set and escalates to buyout (when within cap) instead of re-bidding or abandoning.

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

Suppressed comments (2)

src/AuctionHouseBot.cpp:649

• Log message has an extra space before the comma ("Bought ,"), which makes log searching/aggregation less consistent.

                LOG_INFO("module", "AHBot [{}]: Bought , itemid={}, ah={}, item={}, start={}, current={}, buyout={}", _id, prototype->ItemId, AuctionHouseId(auction->GetHouseId()), auction->item_template, auction->startbid, currentPrice, auction->buyout);

src/AuctionHouseBot.cpp:273

• Buy() silently returns when gBotsId is empty, which can make misconfiguration or init-order problems hard to diagnose at runtime. Consider logging (ideally once) before returning so operators can see why the buyer loop is doing nothing.

    if (gBotsId.empty())
    {
        return;
    }