feat: add chat container

[Killusions]

This adds the chat-container (fully declarative with auto-scroll), potential follow-ups are an ai-chat-container wrapper (model based with a nice signal-based API for streaming / loading state), dogfooded) in #998 (tool message is here #967 )

The chat input is in #948 (merged), the base components (merged) in #877, the file upload directive (merged) in #932

Rough Architecture (ignore the ai chat container for now and the tool message, not a part of this)

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[Killusions]

@panch1739 Take another look please

[github-actions]

Documentation.
Examples.
Playwright report.

Coverage Reports:

• element-ng
• element-translate-ng

[Killusions]

First PR for base components #877

[Copilot]

Pull Request Overview

Copilot reviewed 96 out of 96 changed files in this pull request and generated 3 comments.

Comments suppressed due to low confidence (1)

projects/element-ng/chat-messages/si-markdown-content.component.ts:1

• The first .replace('.', '.') does nothing because it's replacing a literal dot with a literal dot. This should likely be .replace(/\./g, '\\.') to properly escape dots for regex.

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[Killusions]

This (which is now basically just the chat-container) is also now ready for review IMO, it works both in a declarative and model-driven way, with a nice signal-based API for streaming and auto-scroll, which I dogfooded in the Agent.

[Killusions]

Moved the tool message to #967

[Killusions]

@spike-rabbit Split it into a base generic component (which doesn't even need to be AI specific now) and a mostly model-driven wrapper.

Sketched the new Architecture (ignore the tool message, not a part of this)

[Killusions]

Did some improvements and changed it to use the same entrypoint after discussing with @kfenner , will split into two PRs

[Killusions]

@kfenner @spike-rabbit Refactored out the model-API wrapper to #998 , ready to review

[github-actions]

[kfenner]

@Killusions Love it 💜

LGTM 👍

[siemens-element-bot]

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