Preserve Zellij targeting metadata through Safehouse

[clkao]

Safehouse-wrapped sessions preserve Zellij target metadata with one small wrapper-owned default, while leaving generic operator configuration to Safehouse.

What changed

• terminalTargetingEnvArgs() conditionally constructs one static --env-pass=ZELLIJ,ZELLIJ_PANE_ID,ZELLIJ_SESSION_NAME argument.
• Safehouse, not Spacedock, composes repeated named-env flags and SAFEHOUSE_ENV_PASS.
• Claude, Codex, and Pi front doors are unchanged; there is no broad environment inheritance.

Evidence

• Exact-forwarding, scrubbed-absence, and SAFEHOUSE_ENV_PASS composition controls pass.
• A detached mutation that returns no targeting argument breaks the forwarding smoke and wrapper test.
• ZELLIJ=0 go test ./... -count=1 and ZELLIJ=0 go test ./... -race -count=1 each passed 2,168 tests across 17 packages.

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6j state record