#834)

* fix(inference): prevent silent truncation of large streaming responses

The L7 inference proxy silently dropped tool_calls from large streaming
responses due to an aggressive 30s per-chunk idle timeout and a reqwest
total-request timeout that capped the entire body stream. Reasoning models
that pause during "thinking" phases triggered these timeouts, producing
valid-looking but truncated HTTP responses with no client-visible error.

- Extract prepare_backend_request() helper and create a streaming variant
  that omits the total request timeout; body stream liveness is now
  enforced solely by the per-chunk idle timeout
- Add 30s connect_timeout to the reqwest Client builder
- Increase CHUNK_IDLE_TIMEOUT from 30s to 120s for reasoning models
- Inject SSE error events (proxy_stream_error) before the HTTP chunked
  terminator on all truncation paths so clients can detect data loss
- Wrap the streaming relay in BufWriter to reduce per-chunk TLS flush
  overhead
- Bump OCSF severity for streaming truncation from Low to Medium

Closes #829

* fix(inference): drop BufWriter to preserve SSE incremental delivery

The BufWriter introduced in the previous commit buffered SSE frames until
the 16KB capacity filled or the stream ended, defeating incremental token
delivery and potentially reintroducing client-visible timeouts on healthy
streams. Revert to per-chunk write_all+flush but keep the single
format_chunk() call that coalesces framing into one write.

Also fix the streaming integration test: add a 3s mock delay that exceeds
the 1s route timeout so the test actually validates that the streaming
path omits the total request timeout. Previously the mock responded
immediately, passing regardless of timeout behavior.

Closes #783

Only chown read_write paths that the supervisor creates at startup, and leave pre-existing image paths with their original ownership. Add sandbox tests for creation, symlink rejection, and existing-path ownership preservation, and update architecture docs to match the new behavior.

Co-authored-by: John Myers <[email protected]>

* feat(policy): add deny rules to network policy schema

Closes #565

Add L7 deny rules that block specific requests even when allowed by
access presets or explicit allow rules. Deny rules mirror the full
capability set of allow rules (method, path, query params, SQL command)
and take precedence -- if a request matches any deny rule, it is blocked
regardless of allow rules.

This enables the "allow everything except these specific operations"
pattern without enumerating every allowed endpoint. For example, granting
read-write access to GitHub while blocking PR approvals, branch
protection changes, and ruleset modifications.

* fix(policy): deny query matching fails closed, mirror allow-side validation

Addresses PR review findings P1 and P3:

P1: Deny-side query matching now uses fail-closed semantics. If ANY
value for a query key matches the deny matcher, the deny fires. The
previous implementation reused allow-side "all values must match"
logic which allowed ?force=true&force=false to bypass a deny on
force=true.

P3: Deny-side query validation now mirrors the full allow-side checks:
empty any lists, non-string matcher values, glob+any mutual exclusion,
glob type checks, and glob syntax warnings are all validated.

Signed-off-by: John Myers <[email protected]>

format_sse_error only escaped `\` and `"`, leaving two problems:

1. Control characters (`\n`, `\r`, `\t`, and all `\u0000-\u001F`) in
   `reason` produce output that fails `serde_json::from_str` — defeating
   #834's goal of giving clients a parseable SSE truncation signal.

2. An unescaped `\n\n` inside `reason` splits the single error event
   into two SSE frames, letting a misbehaving upstream inject a forged
   frame (e.g. a fake tool_calls delta) into the client's stream. Latent
   today since all in-tree callers pass static strings, but a footgun
   for any future caller passing upstream error text, and the function's
   docstring already invites dynamic reasons.

Replace the manual escape with `serde_json::to_writer` (already a
workspace dep of `openshell-sandbox`). Add unit tests for control
character escaping and SSE event-boundary injection.

Closes #840

Signed-off-by: mjamiv <[email protected]>