Problem: `logger.log` positional args were hard to extend, and adding
`sync` support for pre-block notifications required a clean API. Test
stream completion had no user-visible signal. `setup_contest` could
silently overwrite files when a user's `filename` config returned
colliding paths.
Solution: Replace `(msg, level, override)` with `(msg, LogOpts?)` where
`LogOpts` carries `level`, `override`, and `sync`. Sync path calls
`vim.notify` directly; async path uses `vim.schedule` as before. Add
`on_done` callback to `scrape_all_tests`, fired via `on_exit` and
surfaced as a "Loaded N tests." notification. Detect filename collisions
in `proceed()` before touching the filesystem. Migrate all call sites.
Problem: when required dependencies (GNU time/timeout, Python env) are
missing, config.setup() throws a raw error() that surfaces as a Lua
traceback. On macOS without coreutils the message is also redundant
("GNU time not found: GNU time not found") and offers no install hint.
Solution: wrap config.setup() in pcall inside ensure_initialized(),
strip the Lua source-location prefix, and emit a vim.notify at ERROR
level. Add Darwin-specific install guidance to the GNU time/timeout
not-found messages. Pass capability reasons directly instead of
wrapping them in a redundant outer message.
Problem: the deprecated vim.g.cp_config fallback was kept for
backwards compatibility after the rename to vim.g.cp in v0.7.6.
Solution: drop the shim entirely and update the setup() deprecation
target to v0.7.7.
