fix(swap): abort TAO transfer when receipt parse fails (#297)

[RUNECTZ33]

Summary

Closes #297. S0 funds-stranding bug.

send_tao_transfer() and SubtensorProvider.send_tao() both fell back to the literal string 'tao_transfer' as the tx hash when parsing receipt.extrinsic_hash threw or returned empty:

except Exception:
    tx_hash = getattr(getattr(response, 'extrinsic_receipt', None), 'extrinsic_hash', '') or 'tao_transfer'

The literal then propagated through pending_swap.json, SwapConfirmSynapse.from_tx_hash, and the proof_message 'allways-swap:tao_transfer'. Validators looked up a TAO tx with the hex-decoded version of that literal, found nothing, and the user's funds stranded with no recovery path.

Change

Surface the parse failure as a clean None return at both sites. Both functions already type as Optional[Tuple[str, int]] and the swap flow caller at swap.py:1104-1106 already branches on if send_result is not None, so this fits the existing contract.

Site	Before	After
cli/swap_commands/swap.py:567-577	tx_hash = '...' or 'tao_transfer'	clear console error + return None
chain_providers/subtensor.py:324-333	tx_hash = '...' or 'tao_transfer'	bt.logging.error + return None

Both sites also guard the previously-unhandled "parse succeeded but tx_hash is empty" edge — that path used to leak through to the success branch with an empty-string hash.

Why None and not raise

Issue suggested raise RuntimeError(...). Verified at the call site (swap.py:1104):

for attempt in range(2):
    send_result = send_tao_transfer(...)
    if send_result is not None:
        ...

The retry-loop caller already understands None as a clean failure and retries up to twice. Raising would crash the CLI and lose the retry semantics. None matches the function's existing Optional[...] signature and the existing failure path immediately above (if not response.success: return None).

Scope

allways/cli/swap_commands/swap.py: +14 / -3
allways/chain_providers/subtensor.py: +15 / -3
Total: +29 / -6, two files. No new imports, no signature changes.

Test plan

• Both files AST-parse cleanly (python3 -c "import ast; ast.parse(...)")
• Caller pattern at swap.py:1104 confirmed to handle None (retries up to twice, then exits gracefully)
• No grep hits for 'tao_transfer' literal anywhere else in the repo (git grep "tao_transfer" only matches the function name and the test cassette filenames)
• No callers downstream rely on the bogus literal as a sentinel — all consumers of the returned tuple destructure into (from_tx_hash, ...) and use the hash for chain lookups, so a missing tuple correctly skips that flow