Make the merged repository coherent: README, state, and internal links

The mechanical merge preserved both histories but left two repositories
sitting side by side rather than one repository. This is the part that
makes it whole.

A top-level README explains the three strands - the telescope network
and campaign, the processing code, and in-person observing plans - and
says plainly that image data does not live here, because that is the
first question anyone will have when they find a pipeline with no
pixels.

state/PROJECT.md was still describing a markdown-only reference project
whose scope explicitly EXCLUDED automating bookings and image
processing. Both of those are now most of what the project does, so the
objective, scope and key facts are rewritten to match reality.

state/DECISIONS.md records why the merge happened - the two repos were
split by chronology rather than design, and the seam was already
leaking, with the campaign's TODO citing results held in the other repo
and the pipeline's README explaining a campaign it did not contain. It
also records that the image data deliberately stays out of the
repository.

state/TODO.md gains the pipeline and observing work that previously had
nowhere to live, including the measurement that changes the pipeline
plan: per-frame processing is 2.9 seconds and the whole 24-frame session
is 1.1 minutes single-threaded, so a scheduler earns nothing on stacking
and should be pointed at the Monte Carlo stages instead.

Internal links fixed for the new paths: pipeline/README.md referred to
session-scripts/ throughout, and itelescope/README.md pointed at a
state/ directory that is now one level up.

The .gitignore conflict between the two repositories is resolved by
combining them, with image formats ignored globally except under docs/,
where documentation figures are committed deliberately.

state/DECISIONS.md

@@ -3,6 +3,38 @@
 > 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.
 
+## 2026-07-21: merge itelescope and astro-pipeline into one repository
+
+The two were split by accident of chronology rather than by design. `itelescope`
+began as a reference to the telescope network and grew into the campaign that
+books and runs sessions; `astro-pipeline` was created three hours before this
+merge to hold the processing code once it was moved out of the image directory.
+They describe two halves of one activity, and the seam was already leaking: the
+campaign's TODO referred to processing results held in the other repo, and the
+processing code's README explained a campaign it did not contain.
+
+Merged with **both histories preserved**, by relocating each repository's files
+into a subdirectory in its own history first and then merging the unrelated
+histories. 44 commits, and `git log --follow` still traces a file across the
+move.
+
+Layout: `itelescope/` for the network and campaign, `pipeline/` for the code,
+`observing/` for in-person plans, with the Default Workflow files (CLAUDE.md,
+docs/, state/) at the top level governing the whole repository.
+
+**The old repositories are not deleted.** The drain campaign is live until
+10 Aug with sessions running most nights, and other sessions may be working in
+`itelescope` at the moment of the merge. Both carry a notice pointing here.
+Archive them once the campaign closes, not before.
+
+## 2026-07-21: image data does not live in the repository
+
+A single calibrated frame is 61 MB and a session runs to several gigabytes.
+Sessions stay on disk, organised into named subdirectories, and the code finds
+them through the `ASTRO_SESSION` environment variable. Each session carries its
+own `METHODS.md` describing what was done and what was found, so the account of
+the data travels with the data while the code travels separately.
+
 ## 2026-07-17: follow the Google Sheet, not the support article
 
 The support article (https://support.itelescope.net/support/solutions/articles/247371)