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/DECISIONS.md

@@ -0,0 +1,31 @@
+# Decisions
+
+> A dated, append only log of decisions and their rationale. Newest at the top. Never
+> rewrite past entries; if a decision is reversed, add a new entry that says so.
+
+## 2026-07-17: follow the Google Sheet, not the support article
+
+The support article (https://support.itelescope.net/support/solutions/articles/247371)
+and the maintained Google Sheet
+(https://docs.google.com/spreadsheets/d/1jZWkkjewOuyNC9YzQ8y2d0pO1e4T7EBeysmQMPBVSOk/)
+disagree: the article lists T9, T19, T31, T69, which the sheet omits; the sheet has
+T25, T26, T59, T71-T75, T80, which the article lacks. The article itself points to
+the sheet as the current source, so the review follows the sheet and notes the
+discrepancy. The sheet CSV export is snapshotted in data/ so the review's numbers
+remain reproducible even if the sheet changes.
+
+## 2026-07-17: single review document, not per-telescope files
+
+23 active scopes each need only a spec block and a short assessment; one TELESCOPES.md
+grouped by observatory reads better and is easier to keep current than 23 stub files.
+Revisit if per-scope content grows (photos, session logs).
+
+## 2026-07-17: no launchpad scraping
+
+https://go.itelescope.net/ is an authenticated app shell with no public data. All
+content comes from public support pages and the public sheet; nothing in this repo
+requires iTelescope credentials.
+
+Per-telescope detail pages, if ever needed:
+support.itelescope.net/support/solutions/articles/231901-231920 (older scopes),
+245471 (T68), 251171 (T70), 251556 (T69), 251589 (T19).