fix(chat): wrap long unbroken strings inside chat bubble (#457)

[dolho]

Summary

• Long URLs, base64 blobs, and inline code in chat responses pushed the agent detail page horizontally because text containers did not break unbreakable strings and <pre> blocks grew to their intrinsic width.
• Added Tailwind utilities on all three ChatBubble variants (user / assistant / self-task) so unbreakable strings wrap, <pre> blocks scroll inside the bubble, and inline code/links break at character boundaries.

Closes #457.

Changes

src/frontend/src/components/chat/ChatBubble.vue:

• [overflow-wrap:anywhere] on text containers — wraps long strings (URLs, base64, paths).
• min-w-0 on bubble wrappers — so max-w-[85%] actually clamps width when nested in flex parents.
• prose-pre:max-w-full prose-pre:overflow-x-auto prose-pre:whitespace-pre — <pre> blocks scroll horizontally inside the bubble instead of pushing layout.
• prose-code:break-all prose-a:break-all — inline code and links break at character boundaries.

Pure CSS / template change. No logic changes, no markdown sanitization changes.

Test plan

Verified end-to-end via Playwright (UI agent) against http://localhost:8001:

• Long URL + base64 in user bubble wraps inside indigo bubble
• Pure unbroken base64 string wraps to multiple lines
• Long URL in assistant prose breaks via word-break: break-all on <a>
• <pre> block (2703px content) scrolls inside bubble (overflowX:auto); wrapper scrollWidth == clientWidth
• Inline <code> wraps via word-break: break-all
• No page horizontal scroll in any test (docScrollWidth == docClientWidth == 1280)
• No console errors from ChatBubble.vue compilation
• Normal short messages and markdown rendering unchanged

Manual visual verification: open agent detail → Chat tab on a running agent, paste a long URL + 200-char base64 string, confirm the page does not scroll horizontally and the bubble stays inside its column.

🤖 Generated with Claude Code

[dolho]

Duplicates

#502