feat: read project model from FuseSoC CAPI2 .core files

[hongjr03]

Add a read-only Rust loader for FuseSoC CAPI2 .core files and wire it into Vide's project model. A new crates/fusesoc-model crate parses .core files (preamble stripping, typed serde model with deny_unknown_fields, CAPI2 conditional expressions, *_append normalization, YAML inheritance merge, VLNV parsing, local dependency resolution with cycle detection, and target/fileset expansion into a flat ResolvedProject). The official CAPI2 JSON schema is vendored for reference. Unsupported features (generators, hooks, non-local providers) produce explicit diagnostics rather than being silently ignored. project-model gains ProjectManifest::FuseSocCore / FuseSocCoreDir variants; Workspace::from_fusesoc_core and friends load the resolved project into the existing Workspace / CompilationProfile pipeline. LSP status reporting, qihe, and file watchers are updated accordingly.

Discovery follows a clear precedence: vide.toml with a new [fusesoc] section (explicit core + target + flags) takes priority; otherwise a single .core file is auto-discovered; multiple .core files load as FuseSocCoreDir with auto root-core selection; vide.toml without [fusesoc] keeps the existing sources/libraries behavior. Non-default targets are now reachable via target = "sim" in the [fusesoc] section. 73 tests pass (37 fusesoc-model + 36 project-model).

Closes #337

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Docs preview: https://vide.pascal-lab.net/preview/pr-341/