fix(opencode): declare BadRequest on remaining HttpApi group routes

[TimothyVang]

Summary

• Declares presentation-only error: contracts on HttpApi endpoints that still lacked them after PRs fix(opencode): declare file http query errors #4–fix(opencode): declare BadRequest on event + instance read routes #7 (file, session, provider, project-copy, event, instance).
• Priority groups: experimental (capabilities, session, resource) and tui (open/control routes + showToast).
• Also covers remaining gaps in config, global, mcp, permission, project, pty, question, sync, and workspace.
• Style matches file.ts / provider.ts (HttpApiError.BadRequest); project.directories also declares existing ProjectNotFoundError.

Verify

cd packages/opencode && bun run typecheck
# $ tsgo --noEmit  (exit 0)

Test plan

• Scan all groups/*.ts for HttpApiEndpoint without error: (0 remaining after this PR)
• bun install + bun run typecheck in packages/opencode (pass)
• Pre-push monorepo turbo typecheck (29/29 packages)
• CI green on PR

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