transfer-partners: add Transfer Timing Risks section

[BarnNorth]

Part of a series of improvements from a real transatlantic award booking session (see also #14, #15).

Problem

After finding seats on the target Aeroplan award (LH453 A380 LAX→MUC, 90K Standard), the skill's guidance was to transfer points immediately and book. The skill did correctly flag remaining seat count and note that the risk of losing the space was relatively low — but it gave no warning about transfer timing. Chase's website calls out business day processing, but that warning is easy to miss in the moment. The transfer went in Saturday night before Memorial Day. Even with seats available, not knowing whether points would land before Tuesday — with a 3-day holiday weekend and no way to hold the space since Aeroplan doesn't allow holds — made for an unnecessarily stressful wait. The skill never flagged any of this: no mention of weekend processing delays, no mention that US federal holidays extend the window further, no mention that a newly opened loyalty account adds another 24-72 hours before it can receive transfers.

The only timing guidance in the skill was a single footnote: "Transfers are usually instant but can take up to 48 hours."

Changes

Add a Transfer Timing Risks section covering three scenarios:

1. Weekend and holiday business day delays with a clear rule (transfer before 5pm ET on the last business day before a holiday weekend)
2. Per-program transfer speed reference table (Aeroplan, Flying Blue, United, Hyatt, Turkish, Virgin Atlantic, Alaska)
3. New loyalty account holds — opening a fresh account adds 24-72h before it can receive transfers

Before / After

Before: Single footnote — "Transfers are usually instant but can take up to 48 hours. Don't transfer until you've confirmed award availability."

After: Dedicated section with three named risk scenarios, a per-program speed table, and actionable rules so the user knows exactly when timing becomes a problem before submitting the transfer.

Test plan

• bash scripts/smoke-test.sh --quick — 0 new failures (2 pre-existing on upstream main)
• All 44 skills have valid frontmatter
• README and llms.txt unchanged (no frontmatter edits)