Closes the witness audit-bundle surface. The hash-chain primitive
+ JSONL serializer from earlier iters only handled one event at a
time; this lands the file-stream surface that operations actually
need:
* `WitnessChain::write_jsonl(&mut impl Write) -> io::Result<()>`
— streams every event as one line + `\n`, empty chain writes
zero bytes
* `WitnessChain::read_jsonl(impl BufRead) -> Result<WitnessChain,
WitnessReadError>` — parses event-by-event AND runs chain-level
`verify()` on the loaded chain, catching reordered or replayed
prefixes that per-event hashing alone misses
Critical security property: `read_jsonl` calls `WitnessChain::verify`
on the loaded chain BEFORE returning Ok. A forged bundle assembled
from two valid chains pasted together would slip past the
per-event hash check (each event's `this_hash` is internally
consistent) but the cross-event `prev_hash` linkage detects the
seam. Test `read_jsonl_chain_verify_catches_reordered_events`
locks this — swap two events in a 2-event bundle, see Verify error.
Error surface (new `WitnessReadError` enum):
* `Io { line_no, msg }` — read failure mid-stream
* `Parse { line_no, source }` — per-event from_jsonl_line failure
* `Verify { source }` — chain-level verify failure
`line_no` is 1-indexed so an auditor sees the same number their
text editor shows. Blank lines tolerated for hand-edited bundles.
7 new tests:
* empty chain writes zero bytes
* write→read round-trips a 3-event chain
* exactly N newlines for N events; trailing newline present
* blank lines / leading newline tolerated
* parse error surfaces with correct line_no
* reordered events caught by chain-level verify
* no-trailing-newline still loads the final event
51/51 cog tests green (44 → 51).
Co-Authored-By: claude-flow <ruv@ruv.net>
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