Telescope review: all 23 active iTelescope systems

Adds TELESCOPES.md, a per-observatory review of every telescope on the
iTelescope.net network with a spec block and an assessment for each, a
'choosing a telescope' use-case table, and general observations (CCD to CMOS
migration, Bin2 software limits, elevation limits, network-side calibration).

Data sourcing:
- data/itelescope-telescopes.csv is a verbatim CSV export of iTelescope's
  maintained specs Google Sheet (24 rows: 23 active scopes + T74 placeholder).
- The support article (Freshdesk 247371) supplied observatory groupings and
  minimum elevation limits; it still lists T9/T19/T31/T69 which the sheet has
  dropped - the review follows the sheet and records the discrepancy.
- go.itelescope.net is an authenticated app shell; nothing was scraped from it.

Also fills in the remaining state/ files: TODO (pending: T74 specs, retired
scope reconciliation, periodic sheet refresh), DECISIONS (source-of-truth
choice, single-document structure, no launchpad scraping), NOTES (refresh
command, CSV quirks), ARCHITECTURE (repo layout), and README.

state/TODO.md

@@ -0,0 +1,25 @@
+# TODO
+
+> The current state of play. Keep it honest and current; this is what the next session
+> reads to know what to do. Move items between sections as they progress.
+
+## Done
+
+- 2026-07-17: repo created on git.discworld.casa, Default Workflow scaffold copied in.
+- 2026-07-17: specs sheet snapshotted to data/itelescope-telescopes.csv (24 scopes).
+- 2026-07-17: TELESCOPES.md written: per-scope reviews for all 23 active telescopes
+  plus a choosing guide (T74 noted as in commissioning, no specs published).
+
+## In progress
+
+- (nothing)
+
+## Pending
+
+- Fill in T74 when iTelescope publishes its specs.
+- Reconcile the retired scopes (T9, T19, T31, T69): the support article still lists
+  them but the maintained sheet does not; confirm status and note it.
+- Optional: per-telescope detail pages on support.itelescope.net (links in
+  DECISIONS.md) hold photos and operational history if deeper entries are ever wanted.
+- Periodic refresh: re-export the Google Sheet and diff against data/ to catch new or
+  changed systems.