neoirc-cli wrote its own line when it sent a message, joined or parted,
and ignored the server's event for its own nick, except a JOIN, so a
join showed twice and what the session did from another client never
showed. The HTTP API queues these events to every client of the
session, so the CLI now writes no line of its own when it sends and
shows the event as it shows anyone else's. A direct message the user
sent goes in the recipient's buffer. The user's own part does not mark
the channel unread, as the user has just left it.
Model: opus-5-5
## Summary
Implement SHA-256-based hashcash proof-of-work for `POST /session` to prevent abuse via rapid session creation.
closes sneak/chat#11
## What Changed
### Server
- **New `internal/hashcash` package**: Validates hashcash stamps (format, difficulty bits, date/expiry, resource, replay prevention via in-memory spent set with TTL pruning)
- **Config**: `NEOIRC_HASHCASH_BITS` env var (default 20, set to 0 to disable)
- **`GET /api/v1/server`**: Now includes `hashcash_bits` field when > 0
- **`POST /api/v1/session`**: Validates `X-Hashcash` header when hashcash is enabled; returns HTTP 402 for missing/invalid stamps
### Clients
- **Web SPA**: Fetches `hashcash_bits` from `/server`, computes stamp using Web Crypto API (`crypto.subtle.digest`) with batched parallelism (1024 hashes/batch), shows "Computing proof-of-work..." feedback
- **CLI (`neoirc-cli`)**: `CreateSession()` auto-fetches server info and computes a valid hashcash stamp when required; new `MintHashcash()` function in the API package
### Documentation
- README updated with full hashcash documentation: stamp format, computing stamps, configuration, difficulty table
- Server info and session creation API docs updated with hashcash fields/headers
- Roadmap updated (hashcash marked as implemented)
## Stamp Format
Standard hashcash: `1:bits:YYMMDD:resource::counter`
The SHA-256 hash of the entire stamp string must have at least `bits` leading zero bits.
## Validation Rules
- Version must be `1`
- Claimed bits ≥ required bits
- Resource must match server name
- Date within 48 hours (not expired, not too far in future)
- SHA-256 hash has required leading zero bits
- Stamp not previously used (replay prevention)
## Testing
- All existing tests pass (hashcash disabled in test config with `HashcashBits: 0`)
- `docker build .` passes (lint + test + build)
<!-- session: agent:sdlc-manager:subagent:f98d712e-8a40-4013-b3d7-588cbff670f4 -->
Co-authored-by: clawbot <clawbot@noreply.git.eeqj.de>
Co-authored-by: clawbot <clawbot@noreply.eeqj.de>
Co-authored-by: user <user@Mac.lan guest wan>
Co-authored-by: Jeffrey Paul <sneak@noreply.example.org>
Reviewed-on: sneak/chat#63
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>
sneak
