BUG [Help Model]: Configured width is not respected in edge-case

**Describe the bug**

The `Help` model has a configurable `width` parameter.

The configured `width` is applied when calling the `ShortHelpView` or `FullHelpView` methods on `Help`.

Outside of the herein described edge-case, the `len` of the returned string will be equal to or less than the configured width. However, for both methods, there is an edge-case, resulting in the full string being returned untruncated, with a `len` that exceeds the configured `width`.

This occurs when the leading subset of distinct help items (items in `ShortHelpView` and columns in `FullHelpview`), fit within the configured `width` with a margin of 0-2 (and `width` > 0). In this case, the `shouldAddItem` helper function will not prevent the addition of new items, instead allowing each item to be added to the final string, exceeding the configured `width`. The margin mentioned assumes the configured `Help.Ellipsis` to be of `len==1`: the edge-case margin is equal to [0 - `len(Help.Ellipsis) + 1`].

This might duplicate another [bug](https://github.com/charmbracelet/bubbles/issues/461) that was reported some time ago.

I have prepared a [PR](https://github.com/charmbracelet/bubbles/pull/1032) that fixes the issue and describes more technical detail.

**Setup**

- **OS**: arch Linux x86_64 (kernel 7.1.8-arch1-3)
- **Shell**: fish 4.8.1
- **Terminal Emulator**: ghostty 1.3.1-arch2
- **Terminal Multiplexer**: tmux 3.7c
- **Locale**: en_GB.UTF-8

**To Reproduce**

Steps to reproduce the behavior:
1. Clone to [my fork with fix](https://github.com/wolfwfr/bubbles/tree/fix/help-truncation)
2. Copy `./help/testdata/*` & `./help/help_test.go` into original source-code
3. Execute tests and observe edge-case failure

**Source Code**

See the `Help` model [src](https://github.com/charmbracelet/bubbles/blob/main/help/help.go)

**Expected behavior**

When `width` is configured, one would ideally be able to expect that it is respected in subsequent model method outputs.

**Screenshots**

SHORT HELP VIEW

**BUG**

**FIX**

FULL HELP VIEW

**BUG**

**FIX**

Start with help/help.go, focusing on Help.ShortHelpView, Help.FullHelpView, and the shouldAddItem helper. Review the tests and fixtures in help/help_test.go and help/testdata, including the cases described in PR #1032. Done means both views never exceed a configured positive width, including the documented edge case, with the relevant tests passing.

Written by the indexing model from the issue text.