feat(core): migrate runtime to unity-cli and add unityd daemon

[akiojin]

Summary

• Migrate the repository baseline to unity-cli and remove remaining legacy MCP compatibility paths so maintenance converges on one Rust/TCP implementation.
• Add unityd daemon lifecycle and batch execution paths in the CLI so repeated tool execution can reuse connections and reduce per-call overhead.
• Restrict UNITY_CLI_UNITYD=auto fallback to transport failures only so daemon-reported tool failures are not executed a second time over direct TCP.

Changes

• src/main.rs, src/config.rs, src/transport.rs, src/unityd.rs: add daemon command routing, batch call flow, UNITY_CLI_UNITYD mode handling, and transport-aware fallback/error classification.
• src/lsp.rs, src/lsp_manager.rs: update LSP install/session behavior and retry/error handling for local code-index workflows.
• UnityCliBridge/Packages/unity-cli-bridge/Editor/** and UnityCliBridge/Packages/unity-cli-bridge/Runtime/**: replace legacy MCP naming/paths, refresh handlers/settings/logging, and add missing metadata assets.
• UnityCliBridge/Assets/Editor/UnityCliUiTestSceneGenerator.cs and docs/development.md: standardize generated E2E/UI scene output locations and test guidance.
• .claude-plugin/plugins/unity-cli/skills/**, .codex/skills/**, README.md, CLAUDE.md, docs/**, specs/**: align skill distribution policy and migration/spec documentation with the unity-cli-only direction.

Testing

• cargo fmt --all -- --check — exits with code 0.
• cargo clippy --all-targets -- -D warnings — exits with code 0.
• cargo test --all-targets — all tests passed (54 passed, 0 failed).
• dotnet test lsp/Server.Tests.csproj — Not run in this session because this PR request was completed on the Rust CLI path only.

Related Issues / Links

• None

Checklist

• Tests added/updated
• Lint/format passed (cargo clippy, cargo fmt, svelte-check) — svelte-check is N/A for this repository.
• Documentation updated (if user-facing change)
• Migration/backfill plan included (if schema/data change) — N/A: no schema/data migration was introduced.
• CHANGELOG impact considered (breaking change flagged in commit)

Context

• This branch contains the migration stream from legacy MCP-oriented assets/docs to unity-cli, plus the follow-up daemon fallback fix needed to prevent duplicate side effects after daemon-reported command errors.

Risk / Impact

• Affected areas: Rust CLI command dispatch (src/main.rs), daemon transport (src/unityd.rs), Unity bridge editor handlers/settings, and migration/usage documentation.
• Rollback plan: Revert this PR merge commit to restore prior command routing and docs state; no persistent data migration rollback is required.

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[akiojin]

CI failures were addressed in commits 61db17a and 54baeaa. Local verification completed with: cargo fmt --all -- --check, cargo clippy --all-targets -- -D warnings, cargo test --all-targets. Required PR checks are now passing.

[akiojin]

Resolved develop merge conflicts (notably in src/lspd.rs) and pushed commits 657a19a + 96ece51.

Re-ran local verification with:

• cargo fmt --all -- --check
• cargo clippy --all-targets -- -D warnings
• cargo test --all-targets

Required PR checks are passing.