[evanlinjin]

Adds io::Decoder, a sans-io decoder for Electrum's line-delimited JSON-RPC: feed(&[u8]) the bytes as they arrive, then iterate it for RawIncomings (a batch yields one per message). With io::encode for the other direction, a custom transport only has to move bytes instead of reimplementing line splitting and parsing.

ReadStreamer now uses Decoder, so there's one copy of the framing logic.

Breaking: io::blocking_write, io::async_write and io::tokio_write are removed. Each was just writer.write_all(&encode(msg)); call that instead.

Behaviour changes in ReadStreamer:

• A reader that ends partway through a line now yields an UnexpectedEof error. It used to panic on assert_eq!(b, b'\n').
• An invalid line yields an error, and the stream carries on with the next line instead of ending. Each message is one line, so the next one still parses; whether to stop or skip is the caller's call. The bundled clients still stop at the first error: if the bad line was a response, its request would never resolve.
• Blank lines are skipped.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 92.59259% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 53.55%. Comparing base (8f480f9) to head (7cc4f65).
⚠️ Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
src/io.rs	93.39%	4 Missing and 3 partials ⚠️
src/client.rs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #59      +/-   ##
==========================================
+ Coverage   48.33%   53.55%   +5.21%     
==========================================
  Files          11       11              
  Lines         902      943      +41     
  Branches       18       20       +2     
==========================================
+ Hits          436      505      +69     
+ Misses        461      433      -28     
  Partials        5        5              

Flag	Coverage Δ
rust	53.55% <92.59%> (+5.21%)	⬆️

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