v0.1.0

Added

• Filetype detection for .sou files, in ftdetect/ so that a plugin manager
  can defer the plugin on ft = "souther".
• Buffer settings matching the VS Code extension (// comments, 4-space indent).
• souther-lsp wiring via vim.lsp.config, launched as souther lsp from
  PATH or as java -Xss4m -jar when cmd points at a jar.
• syntax/souther.vim, a fallback for the seconds before the JVM server
  attaches, for buffers it never attaches to, and for machines without
  souther installed. It also covers fake / example / examples for,
  which souther-lsp currently reports as plain variables.
• require("souther").jar_cmd() for building the jar command, and
  require("souther").root() for inspecting root resolution.
• :checkhealth souther reporting Neovim version, the command the client will
  run, the Java runtime, the adequacy option and the resolved workspace root.
• Unit tests (plenary) and CI for Neovim stable and nightly, with all actions
  pinned to commit SHAs. Integration tests run weekly as well as on tags,
  because souther-lsp moves independently of this plugin.

Notes on the design

• cmd is a plain list rather than a function, so cmd_env and cmd_cwd
  reach the server and :checkhealth vim.lsp can show the command.
• The workspace root is resolved upward to the outermost build file, bounded
  by .git. souther-lsp compiles every .sou under its root as one flat
  module set and does not read build files, so the nearest build file is the
  wrong answer in a multi-module tree.
• There is no setup(). vim.lsp.config is the single configuration surface.
• lsp/souther.lua asserts the values it pulls out of lua/souther/. A nil
  raises nothing on its own -- vim.deepcopy(nil) is nil and a nil value drops
  its key from the table -- so the client would otherwise start with no cmd
  at all, visible only as "cmd is a nil" in :checkhealth souther. That check
  now reports a missing cmd as an error, with the stale module cache and the
  duplicate runtimepath entry named as the causes.