CodeQL flags request host and path reaching slog in plugins #1621

Problem

CodeQL (go/log-injection, medium) will flag plugins that pass pctx.Host or pctx.Path to slog.* unsanitized. Both values are client-controlled. pctx.Host comes from the Host header. pctx.Path is the percent-decoded URL path, so a %0A in a request becomes a real newline in the log line.

Call sites, by log message. Line numbers are as of main at 5ba75a0:

• cost/settle (core/cost/settle/settle.go:225, :229) — refused an implausible cost header, refused a cost header larger than any inference call could plausibly be
• a2a-parser (core/plugins/a2aparser/plugin.go:60, :76) — invalid JSON-RPC, not an A2A-namespace method
• context-guru (core/plugins/contextguru/plugin.go:253, :273) — skipped request with no session identity, and the per-request summary line
• cpex (core/plugins/cpex/manager_cpex.go:587) — body modification requested but no protocol extension present
• ibac (core/plugins/ibac/plugin.go:528, :541) — judge uncertain, judge unavailable
• inference-parser (core/plugins/inferenceparser/plugin.go:90) — no/invalid body
• mcp-parser (core/plugins/mcpparser/plugin.go:187, :203, :226, :241) — session terminate, transport stream, body is not valid JSON-RPC, not an MCP-namespace method
• opa (core/plugins/opa/plugin.go:441, :493) — decision error on request, decision error on response
• sparc (core/plugins/sparc/plugin.go:427, :431, :450) — reflector unavailable, failing open, reflector unavailable, failing closed, no inference context to ground against
• token-exchange-aiac (core/plugins/tokenexchangeaiac/plugin.go:414, :418, :424, :458, :462) — audience exists but is not granted to this workload, the destination's client is disabled, token exchange failed (twice), host in another namespace names a target

Status

CodeQL reports only flows that pass through lines a PR changes, so any PR that edits code on a path to one of these sites will raise the alert. #1612 and #1533 had the same problem in the listeners and the session store. Found in review of #1616.

Fix

Wrap each value in pipeline.SanitizeLogValue, the helper #1616 added, which CodeQL recognizes as a log-injection sanitizer. Done when a PR that touches these log lines raises no go/log-injection alerts.