docs: revamp Documentation tab — new framing, audience Quickstart, Sprinter Credit/Liquidity terms

[alexmmueller]

Revamps the Documentation tab. Stacked on docs/api-tab-grouping (PR #212) to avoid mint.json conflicts.

1. New intro framing

introduction.mdx + index.mdx reframed to the current messaging: "programmable credit infrastructure for the onchain economy — we replace overcollateralisation with guardrails." Three value pillars, $300M+/zero-shortfalls proof, lead-with-use-case tone (per the Sprinter Messaging Framework).

2. Community removed

Dropped the Community nav group (stash-points, governance) and the Governance card on the index. De-linked the two /governance references in the contracts page (text kept).

3. Audience-grouped Quickstart

Quickstart is now organised by user:

• Neobanks & Card Programmes (Credit Draw, Card Program) — uses Sprinter Credit
• Wallets — uses Sprinter Credit
• AI Agents — uses Sprinter Credit
• Crosschain Solvers (integration guide) — uses Sprinter Liquidity

Each entry states which API it uses (on the index cards).

4. Terminology aligned

"Sprinter Stash" / "Stash" → Sprinter Credit (credit context) or Sprinter Liquidity (liquidity/solver context) across stash-v1/*, glossary, and audits. Renamed the nav sections "Sprinter Credit (V2)" → Sprinter Credit and "Stash Solver Credit (V1)" → Sprinter Liquidity. Real proper nouns kept (sprinter-stash-contracts repo URLs, spUSDC-LP, SPRNT).

Notes

• Verified locally with mintlify dev — all pages render; removed pages 404; no dangling internal links.
• File paths under stash-v1/ kept (URLs unchanged) to avoid breaking inbound links; only titles/labels/prose renamed.
• The orphan architecture/stash-repayment.mdx (not in nav) still says "Stash" — left untouched; flag if you want it aligned too.

🤖 Generated with Claude Code