feat(truapi): pay withdrawals into their account as getcash does

[filvecchiato]

The payment leg of a withdrawal, as getcash pays its withdrawal key (main c63202a6):

getcash	here
Key wd:eph:<dest>:<n>, counter per wd:<dest>	assign_funding_withdrawal: same label under the funding product, counter wd:<dest>, skipping accounts that hold CASH on People
Payment id: key, then blake2(key ‖ u32le attempt)	funding_attempt_id, shared with top-ups
Page requests the payment; AlreadyExists is success, other errors fail	requested through PaymentPlatform (#1227) as the funding product; a refusal ends the session for a retry
CASH on the key completes payment from any rank-0 state	CASH on the account moves an open, expired, cancelled or payment-failed session to Paid
paymentTaken from the latest status; never expires or cancels	recomputed from the host's latest word on the current attempt; a word on an earlier attempt is ignored
30 min window, expiry only on a chain-read tick	same
Retry: attempt + 1, fresh window, re-sent	retry_funding, while the account is still read (72 h), so CASH that arrived is never asked for twice
Cancel: refused once taken; reads key CASH and host status within 8 s	same, from open, expired or payment-failed; unconfirmed when the host does not answer

Differences: the host's Completed marks the payment taken but the session waits for the CASH on the account before it is Paid. A Paid session is converted and sent on in the next PR.

Part of #1179

[github-actions]

Bundle size report

Compared with main at 02c9712.

	Raw	Gzip	Brotli
truapi-host	7.86 MiB (+71.3 KiB, +0.9%)	5.65 MiB (+24.3 KiB, +0.4%)	5.38 MiB (+19.0 KiB, +0.3%)
truapi-provider	4.03 MiB	1.27 MiB	959.8 KiB
truapi	5.75 MiB (+36.2 KiB, +0.6%)	810.3 KiB (+5.4 KiB, +0.7%)	664.2 KiB (+4.2 KiB, +0.6%)
Total	17.64 MiB (+107.5 KiB, +0.6%)	7.72 MiB (+29.7 KiB, +0.4%)	6.97 MiB (+23.2 KiB, +0.3%)

WebAssembly modules

	Raw	Gzip	Brotli
truapi-host/wasm/web/truapi_server_bg.wasm	2.76 MiB (+70.9 KiB, +2.6%)	986.4 KiB (+24.2 KiB, +2.5%)	745.4 KiB (+18.9 KiB, +2.6%)
truapi-host/wasm/web/truapi_verifiable_bg.wasm	4.89 MiB	4.64 MiB	4.61 MiB
truapi-provider/truapi_provider_bg.wasm	3.99 MiB	1.26 MiB	952.1 KiB

Changed files (10)

	Raw	Gzip	Brotli
truapi-host/wasm/web/truapi_server_bg.wasm	2.76 MiB (+70.9 KiB, +2.6%)	986.4 KiB (+24.2 KiB, +2.5%)	745.4 KiB (+18.9 KiB, +2.6%)
truapi/explorer/codegen/types.js	217.9 KiB (+13.5 KiB, +6.6%)	29.7 KiB (+1.9 KiB, +6.8%)	23.9 KiB (+1.5 KiB, +6.6%)
truapi/playground/codegen/truapi-dts.js	285.2 KiB (+12.4 KiB, +4.5%)	49.1 KiB (+2.1 KiB, +4.6%)	39.6 KiB (+1.7 KiB, +4.5%)
truapi/playground/codegen/services.js	98.0 KiB (+3.4 KiB, +3.6%)	14.7 KiB (+472 B, +3.2%)	12.3 KiB (+362 B, +2.9%)
truapi/generated/types.js	62.8 KiB (+3.0 KiB, +5.0%)	7.7 KiB (+436 B, +5.9%)	6.5 KiB (+338 B, +5.3%)
truapi/generated/client.js	69.0 KiB (+2.5 KiB, +3.8%)	10.3 KiB (+368 B, +3.6%)	8.5 KiB (+317 B, +3.8%)
truapi/generated/wire-decode.js	28.2 KiB (+1.1 KiB, +3.9%)	3.0 KiB (+77 B, +2.6%)	2.5 KiB (+60 B, +2.4%)
truapi-host/generated/host-callbacks.js	10.5 KiB (+432 B, +4.2%)	3.4 KiB (+132 B, +4.0%)	2.8 KiB (+116 B, +4.1%)
truapi/generated/wire-table.js	8.8 KiB (+295 B, +3.4%)	1.5 KiB (+26 B, +1.7%)	1.2 KiB (+19 B, +1.5%)
truapi-host/wasm/web/truapi_server.js	57.8 KiB (+3 B)	10.5 KiB (+3 B)	9.1 KiB (-3 B)

_{Commit: bda3d56}

[github-actions]

CI Status: not green, 1 item needs attention.

• rust: failure

All job results

job	result
android-bindings	success
bundle-size	success
changes	success
changeset-guard	success
cli-package	success
codegen	success
e2e	skipped
explorer	success
headless-install	success
host-android-bindings	success
host-android-detekt	success
host-wasm	success
ios-bindings	success
ios-swift	success
licenses	success
playground	success
provider-android-bindings	skipped
release-guard	success
rust	failure
ts-client	success
ts-debugger	success
ts-host	success
wasm-provider	success
workflow-lint	skipped

Signing credentials: failure as of 2026-10-06, a release may fail

_{Commit bda3d569 · run log}

[filvecchiato]

Consolidated into #1232, which carries these commits.