Make the README more clear and concise

[fern-api]

Summary

Tightens the repository README so contributors can get oriented and running faster, without losing any of the existing guidance.

Changes

• Intro: Replaces the welcome blurb with a one-line description of what this repo is.
• Quickstart: Collapses the nested Prerequisites / Installation / Editing subsections into a single linear flow with one combined shell block. Same commands, fewer headings to scan.
• Writing tips: Trims wordy bullets to their actionable core and removes the Orwell pull-quote so the section reads as a checklist of dos and don'ts.
• Vale section: Reformats the enforced-style list for skimmability; merges duplicate phrasing (e.g., capitalized terminology bullets).
• Getting changes reviewed: Keeps the same routing (issue for new pages / large changes, PR for everything else) in a shorter form.

No content was removed; everything that used to be in the README is still there, just shorter.

Notes

• Net change: ~76 lines removed, ~38 lines added.
• No links, commands, or workflow steps were changed.

Requested by: Fern Support

[fern-api]

Requested by: paarth
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[github-actions]

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