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.

docs-site/content/docs/cli-reference/ktx.mdx

@@ -91,11 +91,11 @@ ktx status
 ktx ingest warehouse
 
 # Build every configured connection
-ktx ingest --all
+ktx ingest
 
 # Search semantic-layer sources and wiki pages
-ktx sl search "revenue"
-ktx wiki search "revenue recognition"
+ktx sl "revenue"
+ktx wiki "revenue recognition"
 
 # Execute read-only SQL
 ktx sql --connection warehouse "select count(*) from public.orders"