init: point VS Code lint and format extensions at .dx/local/bin, the root configs and the Go tier #8517

Editor extensions should run the same pinned binaries and the same config as dx check. Today they use whatever is on PATH and their own defaults. gopls ignores staticcheck.conf (golang/go#36373), so Go needs its tier rendered into gopls settings.

Where

• cli/adopt/src/scaffold.rs:291 (NESTED_SETTINGS), 358-393 (editor_settings_value), 396, 401-470 (merge_owned), 574, 579
• the dx sync staging code for .dx/local/bin (moved by cli: add a .dx/local path module and move managed-environment state under it #8479, IDE paths by cli: move .dx/ide and the tools/dx launcher state under .dx/local #8481)
• quality/tiers/staticcheck/gopls_{standard,strict}.json (from quality: standard and strict tiers for C, C++ and Go (clang_tidy, clang_format, cppcheck, govet, errcheck, staticcheck, gofumpt) #8514)

Do

• Add VscodeKeys for tools that dx sync actually stages under .dx/local/bin:
  • ruff.path, ruff.configuration
  • eslint.runtime/eslint.options.overrideConfigFile
  • biome.lsp.bin, stylelint.configFile
  • shellcheck.executablePath, clangd.path
• Point config keys at the root native file when it exists. Otherwise point them at .dx/config/<tool>/base.*.
• gopls: add gopls to NESTED_SETTINGS and write ui.diagnostic.staticcheck and ui.diagnostic.analyses from the tier's gopls view. Do not write go.vetFlags (gopls ignores it). gopls has no errcheck analyzer; say so in a comment.
• Recommend the matching extension in extensions.json only for selected tools.
• Keep merge_owned semantics: only dx-owned keys change, and user keys survive.

Done when

• In a test workspace with ruff, eslint and Go, settings.json holds the correct paths and gopls keys.
• Editor parity (from quality: standard and strict config profiles in native tool files #7804): a headless check shows the ruff and gopls extensions report the same findings as dx lint on that fixture, and a one-rule edit in root ruff.toml reaches both.
• Rerunning init is a no-op. Removing the tool from selection removes its keys.

Notes

• First verify which tools dx sync stages. Do not emit a path for a binary that is not there.
• Rust editor work stays in rust: upstream a --clippy flag for rules_rust rust_analyzer flycheck #7996, rust: headless flycheck test reports clippy lints on a dx init'd fixture #7998 and rust: pass flycheck --clippy from editor settings and stop writing user_config.json #8366 (paths rebased by cli: move .dx/ide and the tools/dx launcher state under .dx/local #8481).

Part of #8472
Blocked by #8488
Blocked by #8481
Blocked by #8514
Supersedes #7814