v0.1.0 — fix 400 MissingSessionID on opencode / opencode-go

Fixes the 400 MissingSessionID error from opencode.ai's gateway (Console Go) in DeepSeek Harness (dsh).

What it does

• Injects x-opencode-session: <session id> and x-opencode-client: dsh on every opencode / opencode-go request
• Ships as a normal dsh plugin bundle: dsh plugin --profile web add github:BrackRat/dsh-opencode
• No files patched, no settings or credentials touched; the in-memory wrapper re-installs itself on every boot, so dsh upgrades need no action
• Explicitly configured headers still win; becomes a no-op if pi-ai implements the header upstream

Quality

• 9 unit tests (node --test, zero dependencies) run in CI
• Validated end-to-end against a live opencode-go model (DeepSeek V4 Pro / V4 Flash)

Requires dsh >= 0.1.5-rc.1.