feat(instructions): load user-level OpenCode, Codex, and Claude guidance - #1932

Summary

• add runtime-free user Instruction source adapters for OpenCode, Codex, and Claude Code
• compose user guidance before existing project Instructions with canonical-path deduplication
• keep local user roots isolated from Remote workspaces and preserve the injected project filesystem owner
• add bounded traversal, file/content budgets, cache recovery, and redacted prompt labels

Compatibility slice

• OpenCode: global AGENTS.md with Claude fallback, native global config override order, and bounded local exact/glob instructions
• Codex: $CODEX_HOME/AGENTS.override.md with empty-file fallback to AGENTS.md; plugin caches are not scanned
• Claude Code: user CLAUDE.md, config-root-contained imports, and unconditional user rules
• /reload instructions continues to invalidate the Session user-context cache; no watcher is introduced

Architecture and safety

• ecosystem precedence stays in sibling adapters
• reusable bounded local reads stay in services-core
• Product Assembly owns cross-ecosystem order, failure isolation, cacheability, and final prompt composition
• user and project sources share a final 256-file / 2 MiB rendered budget
• Remote workspaces only consume project sources through WorkspaceFileSystem; controller-local user roots are never consulted
• no Plugin Host Runtime dependency, shim, execution path, package cache, network fetch, or generic extension graph is added

Validation

• cargo test -p bitfun-opencode-adapter instruction_source (11 passed)
• cargo test -p bitfun-codex-adapter instruction_source (2 passed)
• cargo test -p bitfun-claude-code-adapter instruction_source (6 passed)
• cargo test -p bitfun-services-core local_instructions (3 passed)
• cargo test -p bitfun-core instruction (20 passed)
• node scripts/check-core-boundaries.mjs
• pnpm run check:repo-hygiene
• cargo check --workspace --exclude bitfun-desktop
• git diff gcwing/main...HEAD --check

The full Desktop workspace check still requires the generated src/mobile-web/dist asset that is absent from this checkout; no placeholder build artifact was created.