[aloneangel45]

Closes #1

Summary

Implements v1.1.0 deterministic Anthropic Messages API & OpenAI SSE streaming recording/replay (pkg/cassette/sse.go), zero-network offline socket enforcement, embedded Go testing.T SDK (pkg/agenttest), bidirectional MCP Content-Length + NDJSON framing, sub-millisecond 100KB fuzzy matching, and TracePort v1.1 split .meta.json + .frames.jsonl session ingestion.

Key Engineering Changes

• Anthropic & OpenAI SSE Streaming Engine (RFC [RFC] Cassette replay support for Anthropic Messages API streaming events #1): Spec-compliant WHATWG SSE decoder/encoder/recorder/replayer in pkg/cassette/sse.go supporting message_start, content_block_start, content_block_delta (text_delta, thinking_delta, signature_delta, input_json_delta, citations_delta), content_block_stop, message_delta, message_stop, ping, error, and OpenAI data: [DONE] streams. Supports instant (0ms CI default), scaled, and exact recorded delta_ms replay modes, plus ReconstructStreamSummary for semantic diffs and exact token accounting.
• Zero-Network Offline Enforcement & Proxy Fixes: Rejects HTTP CONNECT with 403, exposes proxy.NewOfflineHTTPClient blocking non-loopback TCP dials, fixes agentfixture record -- <cmd> server binding, strips outbound Accept-Encoding so upstream gzip responses decode cleanly prior to redaction, releases server mutex prior to I/O & chunk delays, and prefers unconsumed sequence interactions for multi-turn repeated tool calls.
• Canonical Matching, Performance & Redaction Hardening: Canonicalizes raw JSON bodies with 64-bit UseNumber() fidelity, normalizes full URLs and query strings, computes StrictHash after secret scrubbing (eliminating secret hash oracles and allowing dummy CI keys to match), expands secret redaction & CheckForUnredactedSecrets across SSE deltas/headers/URLs/tags while masking matched previews, and optimizes 100KB prompt fuzzy matching from ~15s down to ~0.7ms (336 MB/s).
• Go Testing SDK, MCP Stdio & TracePort v1.1 Interop: Added pkg/agenttest (NewTestServer(t, path)), 16MB MCP StdioRecorder & StdioReplayer with Content-Length + NDJSON framing and automatic initialize/ping/tools/list synthesis, inspect & redact CLI subcommands, -exit-code semantic SSE diffing, and native ingestion of TracePort v1.1 .meta.json + .frames.jsonl sessions.

Benchmark Highlights (CGO_ENABLED=0 go test -bench=. -benchmem ./...)

Benchmark	Latency	Throughput / Allocs
BenchmarkReplaySSEStream_Instant	1.62 us/op	1,587.6 MB/s (22 allocs/op)
BenchmarkDecodeSSE_AnthropicStream	45.58 us/op	225.1 MB/s
BenchmarkStrictMatcher_JSON	9.22 us/op	79 allocs/op
BenchmarkFuzzyMatcher_100KBDisjointPrompt	0.63 - 0.78 ms/op	336.9 MB/s (3 allocs/op)

Verification

• CGO_ENABLED=0 go vet ./... & go test -v -count=1 ./... (71/71 test cases passing across all 8 packages, including 10x consecutive SSE replay determinism)