feat(#8): add GET /items/:id endpoint

[fullsend-ai-coder]

Add a new route handler for GET /items/int:item_id that retrieves a single todo item by its ID. Returns the item as JSON with status 200, or a 404 response with {"error": "item not found"} if the ID does not exist. This follows the same lookup pattern used by the existing PATCH and DELETE handlers.

Changes:

• app.py: add get_item route handler
• test_app.py: add test_get_item and test_get_item_not_found
• README.md: add GET /items/:id to endpoint table

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Closes #8

Post-script verification

• Branch is not main/master (agent/8-get-item-by-id)
• Secret scan passed (gitleaks — 47f7f1511df8ad7036c082d9b2179085cd9ec107..HEAD)
• Pre-commit hooks passed (authoritative run on runner)
• Tests ran inside sandbox

[fullsend-ai-review]

Review

Findings

Low

• [code-organization] app.py:38 — The new get_item handler is placed between create_item (POST) and update_item (PATCH). An alternative ordering would place it after list_items (GET /items) to group GET methods together. However, the current placement groups all /items/:id operations together (GET, PATCH, DELETE), which is also a coherent pattern. Minor preference — either approach is valid.

• [code-organization] test_app.py:28 — Test functions test_get_item and test_get_item_not_found are placed before test_create_item, mirroring the handler order in app.py. Consistent with the handler ordering choice above.

Info

• [logic-error] app.py:30 — Pre-existing: ID assignment uses len(_get_items()) + 1, which produces duplicate IDs after deletions (e.g., create 1, 2, 3; delete 2; create another — new item gets ID 3 again). The new get_item endpoint inherits this — next() returns the first match of a duplicated ID. Not introduced by this PR.

[manish-jangra]

/fs-retro