Make CLI usage easier to grasp with embedded SVG demo

[Qina-ai]

I've added an interactive terminal demo to your README using dg. It walks through a sample command execution to show how the tool works.
What this PR includes
An embedded, recorded terminal demo in the README
.dg/ configuration folder and a GitHub Action for CI validation (optional)
No changes to logic or runtime code
From deepguide.ai

[changeset-bot]

⚠️ No Changeset found

Latest commit: 198d95f

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[asyncapi-bot]

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 No release type found in pull request title "Make CLI usage easier to grasp with embedded SVG demo". Add a prefix to indicate what kind of release this pull request corresponds to. For reference, see https://www.conventionalcommits.org/

Available types:
 - feat: A new feature
 - fix: A bug fix
 - docs: Documentation only changes
 - style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
 - refactor: A code change that neither fixes a bug nor adds a feature
 - perf: A code change that improves performance
 - test: Adding missing tests or correcting existing tests
 - build: Changes that affect the build system or external dependencies (example scopes: gulp, broccoli, npm)
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 - chore: Other changes that don't modify src or test files
 - revert: Reverts a previous commit

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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