Update mint-005 and Add mint-006 through mint-009

[Rob1Ham]

1. MINT-005 Updates: Minor typo fixes and improvements to the existing mint-005.md proposal
2. New Proposals: Adds four new Miniscript template proposals:
   • mint-006.md
   • mint-007.md
   • mint-008.md
   • mint-009.md

mint-006, mint-007, and mint-008 are structurally similar to mint-005, but with variations on the number of keys held by the principal (1 key or 3 keys), and order in which sovereign recovery vs the emergency recovery spend conditions occur. These small changes each result in different expected output descriptor formats.

mint-009 is a multiple agent model on how multiple key agents can hold funds on behalf of a user.

mint-010 is a Custodian Co-Signer vault where a custodian works with a co signer to authorize transactions prior to releasing them, and falling back to recovery keys if cosigner is no longer available.

[apoelstra]

In f571b9f:

ACK MINTs 6 through 8. Haven't finished reading 9 yet. There are a couple minor differences between 5 and the "variants" of 5, most notably that the PKs and PAKs have switched sides in your tables. But the colors are consistent so I think it's fine.

[apoelstra]

ACK f571b9f

MINT 9 looks good to me -- it's much simpler than the other ones.

MINT 10, while mentioned in the description, is not part of this PR.

[Rob1Ham]

Hey @apoelstra - yes originally I had tee'd up a mint-010, but its not needed as of this time.

As for 6-8, of those templates, and how they differ from 005 is to both change the number of signers (3 keys vs 1 key) as well as switch the roles of PKs and PAKs signing order. This is an intentional decision to have vault templates which enable customer's to be able to unilaterally move their bitcoin before a "recovery" spend condition is available, which involves other parties not signing to move funds.

[apoelstra]

as well as switch the roles of PKs and PAKs signing order.

Oof, I totally missed this part! Maybe it needs to be highlighted more? (Or maybe I just need to read more carefully.)

[Rob1Ham]

Pushed fixes since your ACK at f571b9f:

• mint-005: Corrected Layer 2 Example Spend signers from $PK_1$, $PK_2$, $SAK$ to $PK_1$, $PAK_1$, $PAK_2$
• mint-005: actually had incorrect timestamps in the reference transactions, updated those
• mint-006: Fixed stale "10-Key Collaborative Custody Vault" references, as requested added note clarifying the intentional layer reordering and PK/PAK column swap vs MINT-005
• mint-006/007/008: Fixed image alt text from CK to PAK
• mint-009: Fixed key naming in descriptor, policy, and example spend from CK/CSK to PAK/SAK (body of document already used PAK/SAK)