Docs: Start Here quickstart for wallet, miner, and developer paths

[Scottcjn]

Summary

RustChain needs one short, opinionated Start Here entry point so a new user can get useful results in the first 10 minutes without hopping across README sections, issues, and bounty threads.

Deliverable

Create a single quickstart document such as START_HERE.md and link it prominently from the main README.

Required Paths

The quickstart must cover exactly these three newcomer paths:

1. wallet / user
2. miner
3. developer

Scope

• Add one clear quickstart entry point.
• Use copy-pasteable commands for each path.
• Tell users where to check health / status.
• Tell users where bounty claims and wallet registration belong.
• Explain that RustChain payout wallets are RustChain wallet names / IDs, not ETH / SOL / Base addresses.
• Call out any self-signed TLS or -k caveats where they actually apply.

Acceptance Criteria

• The main README links to the quickstart in an obvious place.
• The guide has separate wallet, miner, and developer sections.
• Every command shown in the guide was tested before merge.
• The guide distinguishes RustChain wallet IDs from external-chain addresses.
• The guide points users to rustchain-bounties for claims / payout flow.
• The guide does not introduce risky shortcuts such as curl | bash.

Non-Goals

• replacing full documentation
• writing a full API reference
• covering every advanced miner or node configuration

Claim Routing

Implementation discussion belongs here. Bounty proof / payout claim belongs in Scottcjn/rustchain-bounties#1493.

[Scottcjn]

This issue now has an onboarding bounty attached in Scottcjn/rustchain-bounties#1493.

If you pick this up, claim the bounty there and reference this issue in your PR.

[Scottcjn]

Scoping this parent into narrower child issues:

• #706 Start Here doc skeleton + README entrypoint
• #707 verify wallet / miner / developer quickstart commands against current flow

If you open a PR against one of these slices, reference both the child issue and this parent issue.

[Scottcjn]

Board treatment update: this parent is now an umbrella/spec card. For direct contributor work, prefer the child issues #706 and #707 unless the parent spec itself needs to change.