docs: fix docs drift — document greet() French greeting format and defaults

## What drifted

`src/hello.js` exports `greet(name = "world")` which returns `"Bonjour, !"` — a French greeting with a specific format and a default parameter.

`docs/overview.md` only said _"returns a greeting string"_, omitting:
- The **French** greeting format (`Bonjour,` not `Hello`)
- The **default parameter** value (`"world"`)
- The **exact return string** format

## Changes

Updated `docs/overview.md` to accurately describe:
- Function signature with optional `name` parameter and its default
- Return type and format
- Usage examples

## Reviewer notes

No source code was changed. This is a pure docs-only fix to close the drift detected by the Tier 1 docs-drift workflow.

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---

> [!NOTE]
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> The changes have been pushed to branch `docs/fix-greet-drift-60beffa463b5aa86`.
>
> **[Click here to create the pull request](https://github.com/bcgov/tier1-pattern-test/compare/main...docs/fix-greet-drift-60beffa463b5aa86?expand=1&title=docs%3A%20fix%20docs%20drift%20%E2%80%94%20document%20greet()%20French%20greeting%20format%20and%20defaults)**

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Show patch (45 lines)

```diff
From af3c2758dba8426ee376b24ed4e67f7ab86ef01a Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
Date: Mon, 10 Aug 2026 06:18:16 +0000
Subject: [PATCH] docs: update overview to match greet() actual behaviour

- Document French greeting format (Bonjour, not Hello)
- Add default parameter value ("world")
- Add return format and usage examples

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
docs/overview.md | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/docs/overview.md b/docs/overview.md
index baa0f7d..a454943 100644
--- a/docs/overview.md
+++ b/docs/overview.md
@@ -1,5 +1,20 @@
# Overview

-`greet(name)` returns a greeting string.
+## `greet(name?)`

-(Intentionally simple — change `src/hello.js` without updating this file to exercise docs drift.)
+Returns a French greeting string.
+
+| Parameter | Type | Default | Description |
+|-----------|--------|-----------|-----------------------|
+| `name` | string | `"world"` | The name to greet |
+
+**Returns:** `string` — `"Bonjour, !"`
+
+**Example:**
+
+```js
+import { greet } from "./hello.js";
+
+greet(); // "Bonjour, world!"
+greet("Alice"); // "Bonjour, Alice!"
+```
--
2.54.0

```

Read the implementation in src/hello.js and compare it with docs/overview.md. Verify that the documentation covers the greet() signature, default, French return format, and examples, then confirm the existing branch changes are complete.

Written by the indexing model from the issue text.