Empty positions in [dependencies], [features], [generated_files],
[capabilities], [xlings.workspace], [xlings.envs] and [tools.overrides]
now offer snippet templates of the common forms instead of nothing.
Also use Folder/EnumMember/Snippet completion item kinds so section,
key and value suggestions render with fitting icons.

Add key completions for [build.cxx_runtime] (default/tests),
[resources.version-info] and [runtime."<cap>"] (provider), and the
[build].profile alias of default-profile, all per docs/zh/05-mcpp-toml.md.

Offer glob/cflags/cxxflags/asmflags/defines inside [build].flags and
feature flags inline-table entries (docs/zh/05-mcpp-toml.md section
2.3/2.8). SectionSpec no longer carries key data; section lookup reads
SECTION_GROUPS only.

Bare dotted dependency keys (capi.lua, imgui.backend.glfw_opengl3)
now parse as key=value positions instead of falling back to template
suggestions. Sections are tri-state: document top offers section
headers, unknown custom sections offer nothing (appendix A: custom
toml keys are unsupported), known groups offer their keys.

The mcpp.toml field set spans more than docs/zh/05-mcpp-toml.md:
- [workspace] members/exclude and [workspace.dependencies] with
  namespace subtables (06-workspace.md)
- [package].namespace and the dependency spec workspace = true
  inheritance key (06-workspace.md)
- [toolchain] per-platform pins linux/macos/windows and
  [build].target with the documented target vocabulary
  (03-toolchains.md)
- linkage = "dynamic" alongside static (03-toolchains.md)

[pack] default_mode/include/exclude and [pack.bundle-project]
also_skip/force_bundle per docs/zh/02-pack-and-release.md. All zh docs
(00-10) are now swept for mcpp.toml sections; no others define new
manifest tables.

New mcpp.tomlCompletion boolean setting (resource scope, default
false); the completion provider returns nothing until it is enabled.