refactor(plugins): load OpenCode adapters from managed packages - #1525

Summary

• Replace the public OpenCode workspace-scanning factory with one factory that consumes validated BitFun-managed package input.
• Load only the selected managed package after source approval, preserving containment, no-follow, hash, operation-budget, and final trust checks without letting unrelated invalid packages block the read.
• Keep source approval separate from Host activation: managed inputs remain unactivated read-only projections and cannot produce effects.
• Align the product architecture, composition-root sequence, Host design, OpenCode audit, module guidance, and boundary checks with the implemented scope.

Behavior and boundaries

• Production Product Assembly binding, activation UI, Host trust issuance, JS/TS execution, npm installation, hooks/events, and final tool registration remain out of scope.
• Existing user or global OpenCode directories are not scanned. A future import flow must convert them into the same managed-package format.
• PluginPackageInput validates manifest/source identity, exact file set, per-file and package size limits, and hashes. It is self-consistent input, not an approval credential.
• Selected-package reads ignore unrelated package content, serialize retained-content loads per service instance, and report transient capacity, trust-store, and trust-race failures as retryable unavailability.
• Local, npm, invalid-config, and empty-package projections use bounded source-derived IDs with a 128-bit digest; duplicate npm declarations are removed.
• Packages with no supported OpenCode entry return a typed diagnostic instead of an empty projection.
• Current source inspection is limited to the tested single-line declaration subset. It is not a general JavaScript or TypeScript parser, and other syntax is outside this PR's compatibility claim.
• Invalid external content remains diagnosable and cannot crash, execute code, or produce effects.

Resource and code-size impact

Verification

• cargo +nightly test -p bitfun-product-domains --test plugin_source_contracts --features plugin-source (7 passed)
• cargo +nightly test -p bitfun-services-integrations --no-default-features --features plugin-source plugin_source --lib (40 passed)
• cargo +nightly test -p bitfun-opencode-adapter (30 passed: 15 unit + 15 Host integration)
• node --test scripts/check-core-boundaries.test.mjs (3 passed)
• node scripts/check-core-boundaries.mjs
• pnpm run check:repo-hygiene
• cargo +nightly check --locked --workspace --exclude bitfun-cli
• git diff --check

The workspace check retains pre-existing Windows unsafe-op-in-unsafe-fn warnings and introduces no new warning class.

Independent review

Fresh isolated architecture/product and Rust security/performance reviewers audited the rebased full diff. Findings covering composition-root direction, empty projections, source-ID collisions, target-load isolation, retryable error semantics, misleading candidate documentation, and unnecessary reconciliation parameters were fixed. After the scope was explicitly limited to managed fixed input and read-only diagnostics, both reviewers reported no remaining P0/P1/P2 findings.