Seed default config on install; share defaults JSON with runtime

The defaults now live in a single file, scripts/config.default.json:

- src/config.ts imports it via 'with { type: "json" }' and derives
  DEFAULT_CONFIG (with seconds->ms conversion at the boundary), so the
  CLI help text always matches what the seeded user config contains.
- scripts/install.sh copies the same file to
  $XDG_CONFIG_HOME/move/config.json only if no file is already there.
  Existing configs (yours or from a previous install) are never
  overwritten.
- scripts/uninstall.sh does not touch the user config file at all,
  following the strict Unix convention. It does print a one-line
  notice pointing at the path so the user can rm -rf the dir
  themselves if they want a fully-clean removal.
- tsconfig.json gains resolveJsonModule:true so tsc accepts the JSON
  import.
- A small runtime assertion in src/config.ts (assertSeedShape) fails
  loudly if the seed file is missing keys or has wrong types.
- README Configuration section documents the seed behavior; Uninstall
  section documents the leave-config-behind policy with the rm-it-
  yourself command; Files table gains scripts/config.default.json.

README.md

@@ -67,6 +67,15 @@ curl -fsSL https://gitea.cahlen.com/nokeo08/Move/raw/branch/master/scripts/unins
 Removes the wrapper at `$XDG_BIN_HOME/move` and the install tree at
 `$XDG_DATA_HOME/move`. Bun stays — it's your runtime, not ours.
 
+Your config file at `$XDG_CONFIG_HOME/move/config.json` is **intentionally
+left behind**, whether you customized it or never touched the seeded
+defaults. The uninstaller prints a one-line notice pointing at the path
+so you can remove it manually if you want:
+
+```sh
+rm -rf "${XDG_CONFIG_HOME:-$HOME/.config}/move"
+```
+
 ## Usage
 
 ```text
@@ -109,7 +118,13 @@ error to `stderr` and exits with code `2`.
 ${XDG_CONFIG_HOME:-$HOME/.config}/move/config.json
 ```
 
-If the file is missing, defaults are used (no config file is required).
+The installer seeds this file with the default values on a fresh install,
+**only if no file already exists at that path**. Existing configs — yours
+or from a previous install — are never overwritten. If you remove the
+file later, `move` still works: missing defaults fall back to the values
+baked into the binary (which match what was seeded, since both come from
+`scripts/config.default.json`).
+
 Pass `-C` / `--config <path>` to point at a different file; in that mode
 the file must exist.
 
@@ -252,12 +267,13 @@ move --help
 
 | File                | Purpose                                                                       |
 | ------------------- | ----------------------------------------------------------------------------- |
-| `scripts/install.sh`   | End-user installer; curl-pipeable from Gitea.                              |
-| `scripts/uninstall.sh` | End-user uninstaller; curl-pipeable from Gitea.                            |
-| `scripts/dev-setup.sh` | Contributor bootstrap (verify Bun + `bun install`).                        |
+| `scripts/install.sh`         | End-user installer; curl-pipeable from Gitea.                        |
+| `scripts/uninstall.sh`       | End-user uninstaller; curl-pipeable from Gitea.                      |
+| `scripts/dev-setup.sh`       | Contributor bootstrap (verify Bun + `bun install`).                  |
+| `scripts/config.default.json`| Single source of truth for default values: imported by `src/config.ts` and copied to `$XDG_CONFIG_HOME/move/config.json` on a fresh install. |
 | `src/move.ts`       | CLI entry point: parses args, dispatches help/version, starts the loop.       |
 | `src/cli.ts`        | Argument parsing, validation, and help/version output.                        |
-| `src/config.ts`     | `Config` type (carries every tunable, including `verbose`), `DEFAULT_CONFIG`, `defaultConfigPath`, and the layered `resolveConfig` overlay. |
+| `src/config.ts`     | `Config` type (carries every tunable, including `verbose`), `DEFAULT_CONFIG` (derived from `scripts/config.default.json`), `defaultConfigPath`, and the layered `resolveConfig` overlay. |
 | `src/configFile.ts` | Optional JSON config-file loader with strict schema validation.               |
 | `src/keeper.ts`     | Synthetic-activity sweep and idle-watch loop.                                 |
 | `package.json`      | Bun project manifest. Single runtime dep: `@nut-tree-fork/nut-js`.            |