keepClientCwd misses Primary working directory form — env cwd dropped from scrubbed prompt #21

Title: keepClientCwd misses Claude Code's "Primary working directory:" form — env cwd dropped from scrubbed prompt

Problem

scrubOpencodeFingerprints's OPENCODE_ENV_BLOCK replacement calls keepClientCwd, whose capture regex is:

/(?:^|\n)[ \t]*Working directory:[ \t]*([^\n<]+)/i

Claude Code's env block emits Primary working directory: (newer sessions format). The line-start anchor plus exact label means the capture misses that form, keepClientCwd returns "\n", and the kept <env> block loses the working directory entirely.

Consequence

Every consumer that reads the client working directory from the scrubbed system prompt loses it. In Meridian specifically, sessions keyed from the prompt degrade — Meridian's own diagnostics warn about exactly this class of loss:

The directory is read from the <env> block of the system prompt; a plugin implementing experimental.chat.system.transform (for example opencode-scrub) may have removed it.

It also degrades the model's own project-context awareness (no cwd visible in the prompt).

Fix

Make the capture accept the optional Primary prefix:

const cwd = block.match(/(?:^|\n)[ \t]*(?:Primary[ \t]+)?Working[ \t]+directory:[ \t]*([^\n<]+)/i)?.[1]?.trim();

Verified locally against the published dist (0.2.3): legacy Working directory: form still captured, Primary working directory: now captured (case-insensitive), all other scrub rules unaffected (identity/omo-env/fingerprint removal identical), and a live round-trip through the bridge confirms the model sees the cwd while fingerprints remain scrubbed.

Happy to send the PR with tests if the fix shape looks right.