AlgoScan

This is still going to fail its own tests until the sdk is updated,
and the pin is moved forward, but the sdk cant be updated until this
is.  (At least that appears to be the required merge order)

* Don't allow filtering on the pq signatures

Catalog:
- Add 25 Algorand open-source repos from the deep-research report
  (algorandfoundation ×5, algorandecosystem ×6, algorand-devrel ×1,
  asastats ×3, TxnLab ×1, pactfi ×1, gabrielkuettel ×1, blockmaker-ai ×1,
  astro-explorer ×1, fhish-tech ×2, brandonjsellam-Releone ×1,
  AbaloneLabs ×1, michaeltchuangllc ×1)
- Total tracked repos: 2,634 → 2,659 (zero duplicates, CI-validated)

Documentation:
- README.md: add Signals/ to repository layout tree, add .gitignore,
  update PR scope policy to accept both catalog and signal PRs,
  add Signals section (what belongs, how to add, signal ≠ catalog entry)
- PULL_REQUEST_TEMPLATE.md: add PR type selector (tracked repos vs signal),
  add signal article checklist, add signal title format
- CODEOWNERS: add explicit Signals/ ownership rule

If you'd prefer to split into two commits (catalog vs docs), here's an alternative pair:

Commit 1 (catalog):
📦 Add 25 new Algorand tracked repos from deep-research report

Repos added across 13 GitHub owners (9 new, 4 existing):
algorandfoundation, algorandecosystem, algorand-devrel, asastats,
TxnLab, pactfi, gabrielkuettel, blockmaker-ai, astro-explorer,
fhish-tech, brandonjsellam-Releone, AbaloneLabs, michaeltchuangllc

Total: 2,634 → 2,659 entries.

Commit 2 (docs):
📝 Document Signals workflow in README, PR template, and CODEOWNERS

- README: add Signals/ to layout tree, update PR scope policy,
  add Signals section with contribution guidelines
- PR template: add PR type selector and signal article checklist
- CODEOWNERS: add explicit Signals/ ownership rule

This work was originally made with claude assistance and adapted from there.