feat(cli): smart defaults and flatter command surface for ktx (#177)

Bare invocations now do the obvious thing instead of erroring out, and mode-as-subcommand patterns collapse into flags on the parent. No new top-level commands.

- `ktx ingest` (bare) ingests every configured connection. The `text` subcommand is gone; capture inline notes with `ktx ingest --text "..."` and files with `ktx ingest --file path` (use `-` for stdin). `--text`/`--file` reject a positional connection id; pass `--connection-id` to tag captured notes.
- `ktx connection` (bare) lists; `ktx connection test` (bare) tests every configured connection.
- `ktx wiki` and `ktx sl` flatten `list`/`search`: bare lists, with a `[query...]` positional searches (multi-word joined with spaces). `sl validate` and `sl query` stay as distinct verbs and now read `--connection-id` from the parent.
- `ktx mcp` (bare) prints daemon status.

Adds a shared `resolveConnectionSelection` helper consumed by ingest and connection test. Updates README, docs-site cli-reference and guides, next-steps strings, agent SKILL templates, and all affected tests. Per-package type-check, unit tests (605), smoke tests, and dead-code checks all pass.

packages/cli/src/commands/connection-selection.ts

@@ -0,0 +1,18 @@
+export type ConnectionSelection =
+  | { kind: 'all' }
+  | { kind: 'single'; connectionId: string };
+
+export interface ResolveConnectionSelectionInput {
+  connectionId?: string | undefined;
+  all: boolean;
+}
+
+export function resolveConnectionSelection(input: ResolveConnectionSelectionInput): ConnectionSelection {
+  if (input.all && input.connectionId !== undefined) {
+    throw new Error('--all cannot be combined with a connection id argument');
+  }
+  if (input.connectionId !== undefined) {
+    return { kind: 'single', connectionId: input.connectionId };
+  }
+  return { kind: 'all' };
+}