Fix/issue 82 provider bootstrap

[GraDea]

Summary

Fixes the remaining issue #82 bootstrap regression by keeping OpenCode provider/OIDC code out of the plugin-loader bundle.

This restores lazy loading for the OpenCode provider path and defers @opencode-ai/sdk/v2/client until runtime provider use, so plugin startup does not eagerly pull SDK/OIDC internals such as @vercel/oidc / getVercelOidcToken.

Changes

• Added a lazy loadOpencodeProvider() boundary for provider call sites.
• Changed plugin startup host transport setup to load provider code only when needed.
• Added a lazy SDK client wrapper so @opencode-ai/sdk/v2/client is imported only on runtime SDK use.
• Updated auto-capture/user-profile provider call sites to use the lazy loader.
• Added bundle-boundary regression tests for:
  • transformer/sharp bootstrap safety
  • OpenCode SDK/OIDC absence from plugin-loader bundle
  • bundled lazy provider loader runtime resolution

Testcase for issue #82

Automated regression

bun run build
bun test tests/plugin-bundle-boundary.test.ts
Expected: plugin-loader bundle does not contain:
- @opencode-ai/sdk/v2/client
- node_modules/@opencode-ai/sdk
- @vercel/oidc
- getVercelOidcToken
- transformer/sharp internals
Full verification run
bun run build
bun run typecheck
bun test tests/plugin-bundle-boundary.test.ts tests/plugin-host-config.test.ts tests/opencode-provider.test.ts tests/auto-capture.test.ts
Result: 29 passing tests.
Real OpenCode runtime check
Configured OpenCode to load this branch directly:
{
  "plugin": ["/home/peshkov/src/opencode-mem"]
}
Then cleared logs, started a fresh OpenCode session, and triggered auto-capture.
Observed result:
Auto-capture memory persisted
No bootstrap crash from provider/OIDC, no getVercelOidcToken startup failure, and no auto-capture provider fallback in the branch retest.
Notes
OpenCode still logs schema rejection warnings on both main and this branch, but auto-capture persists successfully on both. Those warnings are not introduced by this change and do not block the issue #82 bootstrap fix.