Timelock: direct-archive caveat, ARCHITECTURE.md cleanup

[0xNeshi]

This is just a partial review of #47 .

Changes

Cancellers do not bound direct archives

• packages/security/api-timelock-v1/README.md now states that cancellers does not limit who can remove an operation, because its signatories can always call Archive directly. It also says to use the timelock's full signatory set if no single signatory may remove an operation alone.
  Why: Daml always gives signatories an Archive choice, so integrators need to know about it and size the signatory set themselves.

ARCHITECTURE.md

• Moves the "choice body calls a method that calls a library function" rationale out of the Timelock section into a general section, with a link to the Splice TransferFactory_Transfer example and a pointer to Checked.
  Why: the pattern applies to any component with interfaces, not only Timelock.
• Removes Timelock paragraphs that repeated package README.md content: package contents, lifecycle authority, and the three-contract integration layout.
  Why: ARCHITECTURE.md holds design rationale. Usage and behavior belong in the package README.md files.
• Drops the Pausable and Timelock state examples from the migration paragraph and formats Pausable and pause as code.
  Why: the migration paragraph applies to any contract state, so the component-specific examples were not needed.