#35890 doc: use overwrite (>) instead of append (>>) for one-shot PSBT files in offline-signing-tutorial.md

• Prevent tutorial users from breaking subsequent commands when re-running offline signing steps
• Avoid accumulating duplicate PSBT lines in output files when commands are repeated without manual cleanup

Updates `doc/offline-signing-tutorial.md` to use file overwrite (`>`) rather than append (`>>`) when redirecting `bitcoin-cli` output to `funded_psbt.txt` and `final_psbt.txt`. When steps are executed more than once without deleting intermediate files, append adds extra lines that cause downstream `$(cat ...)` invocations to break with argument-splitting errors.

Problem: Users re-running steps in the offline signing tutorial encounter command errors because multiple PSBT strings end up in single-value text files. This affects developers and node operators following the tutorial.

P4 · bug fix

• P4 because it fixes a minor usability issue in an instructional markdown document
• Prevents command-line argument errors without altering critical security advice

Fixes a minor issue in tutorial documentation where repeating a step without deleting intermediate files causes command failures. While useful, it is narrow in scope and has minimal claim on scarce reviewer time.

Membership: Modifies doc/offline-signing-tutorial.md to fix shell redirection operators.

Factors: security/stability 0, bug 1, performance 0, user value 1, leverage 0

P4 · cleanup

• P4 because it touches tutorial documentation rather than wallet implementation or RPC logic
• Carries no impact on fund safety, descriptor handling, or transaction creation

Does not alter any wallet source code, wallet logic, or RPC interfaces, only updating documentation examples.

Membership: Carries the maintainers' Wallet label and addresses the offline signing workflow with wallet RPCs.

Factors: security/stability 0, bug 0, performance 0, user value 1, leverage 0

• Ready for review with a minimal diff, no conflicts, and passing CI

The patch is small (+2/-2 in one markdown file), applies cleanly, and has no pending technical requests.

Author status: silent since 2026-08-12 after rewriting the description

Resolved concerns:

• davidgumberg noted the issue and PR description appeared to be LLM-generated in violation of project AI policy; the author rewrote both in their own words.

• No technical review comments or ACKs submitted yet
• Procedural objection about AI-generated text was resolved by rewriting the description (davidgumberg)

Neutral; davidgumberg raised an AI policy objection which the author addressed by rewriting the description

Nobody has yet reviewed or ACKed the code change itself. The only feedback was a process objection regarding LLM-generated text, which the author resolved by rewriting the description.

• 2026-08-12 davidgumberg asked for the description to be rewritten under the AI policy
• 2026-08-12 GuTS805 rewrote the description and requested re-review

Objections:

Participants: davidgumberg (objection)

State derived from the lists: objections resolved, nobody has spoken for the PR

Review verdicts (DrahtBot): 0

0 lines under test/bench/ci.

• doc/offline-signing-tutorial.md +2/-2

This PR modifies doc/offline-signing-tutorial.md to use overwrite redirection rather than append when saving PSBT output to text files. This prevents subsequent commands using unquoted $(cat ...) from failing with argument-splitting errors if steps are run repeatedly. It is a minor documentation bug fix with no code changes. An initial objection regarding an LLM-generated description was resolved when the author rewrote it, but the PR has received no technical review yet.