## Context

The kb client currently overloads the root Cobra command to handle both command dispatch and implicit note ingestion. Any unrecognized multi-word input is silently submitted as a note via `POST /api/v1/jobs`. This was introduced to reduce friction for note-taking but has proven error-prone — typos in commands create unwanted notes. A single-word guard was added but multi-word typos still slip through.

The root command has: custom `ArbitraryArgs` validation, a `RunE` with arg-count branching, a `--tags` flag for the note shorthand, a custom usage template with `isRootCmd` template function, and `submitNote()` living in `add.go`.

## Goals / Non-Goals

**Goals:**
- Eliminate accidental note creation from mistyped commands
- Provide a clean, explicit `addnote` command that pairs with existing `addfile`
- Revert root command to standard Cobra behaviour (no custom args, no custom template)
- Keep the same API contract — `POST /api/v1/jobs` with `note` field unchanged

**Non-Goals:**
- Changing the engine API
- Modifying `addfile` behaviour
- Adding new content types (url, bookmark, etc.)
- Backward compatibility shim for `kb "text"` syntax

## Decisions

### 1. New `addnote` command in its own file

Create `client/cmd/addnote.go` with a `cobra.Command` that takes `ExactArgs(1)` — a single quoted string. This mirrors `addfile` which also takes `ExactArgs(1)`.

**Rationale**: Keeps each command in its own file (consistent with the existing pattern). `ExactArgs(1)` means the user must quote multi-word notes, which is unambiguous and avoids the flag-parsing edge cases that plagued the implicit shorthand.

**Alternative considered**: Joining `ArbitraryArgs` like the old shorthand. Rejected — this is exactly the ambiguity we're removing.

### 2. Move `submitNote()` from `add.go` to `addnote.go`

The function is only used by the addnote command, so it belongs in the same file.

**Rationale**: `add.go` becomes purely about file operations (it already is, aside from hosting `submitNote()`). Clean separation.

### 3. Fully revert root command to Cobra defaults

Remove: `ArbitraryArgs`, custom `RunE` (replace with nil — Cobra shows help by default), `--tags` flag on root, custom usage template, `isRootCmd` template function.

**Rationale**: The root command should do one thing — dispatch to subcommands. All the custom logic was there to support the implicit shorthand which is being removed.

### 4. `addnote` gets its own `--tags` flag

The `--tags` flag moves from the root command to `addnote`, matching how `addfile` already has its own `--tags` flag.

## Risks / Trade-offs

- **Breaking change for existing users** → Mitigated by clear error messaging. If someone types `kb "some text"`, Cobra will say "unknown command". The `examples` command will show the new syntax.
- **Slightly more typing for notes** (`kb addnote "text"` vs `kb "text"`) → Acceptable trade-off for eliminating accidental ingestion. Tab-completion helps.
- **Scripts using old syntax will break** → This is intentional. The old syntax was a foot-gun.