Docs: use topic-aligned data/<topic-path>/ ingest paths and add nested-topic examples (fixes #18 and #19)

[nsuruguay05]

Description

Updates the documentation to use topic-aligned ingest file paths under data/<topic-path>/ and adds nested-topic ingestion examples so the documented file layout matches the topic hierarchy used by the Content API.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring (no functional changes)

Related Issues

Fixes #18
Fixes #19

Changes Made

• Updated README.md ingest examples to use topic-aligned paths such as ./data/documentation/*.pdf.
• Added nested-topic ingest examples using slash-separated topic paths such as documentation/tutorials and matching file locations such as ./data/documentation/tutorials/*.pdf.
• Updated docs/commands.md to explain the topic-aligned data/<topic-path>/ workflow and nested-topic path format.
• Updated docs/getting-started.md examples to use topic-aligned ingest directories and added a nested child-topic example.
• Added a changelog entry in CHANGELOG.md for the documentation update.

Testing Done

• Unit tests pass locally
• Added new tests for new functionality
• Tested manually

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes