feat!: installation only from a release, into an empty folder; upstream merge/verify and private-instance.md removed, dist adopt, shell-neutral instructions (#153)

Files changed:
- .gitea/workflows/ci.yml
- .gitea/workflows/release.yml
- AGENTS.md
- CHANGES.md
- DEVELOPMENT.md
- EVALS.md
- INSTALL.md
- README.md
- VERSION
- docs/ownership-and-templates.md
- instructions/CONTRACT.md
- instructions/bootstrap.md
- instructions/dev/dev-setup.md
- instructions/dev/stack-dev/SKILL.md
- instructions/gates.md
- instructions/ingest-large-tree.md
- instructions/kb-profiles.md
- instructions/mcp-read-server.md
- instructions/migrations/3.0.0-authoring-conventions.md
- instructions/preflight.md
- instructions/private-instance.md
- instructions/session-setup.md
- instructions/setup-instance.md
- instructions/upgrade-instance.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/cli.py
- tools/chemenu/cli_contract.py
- tools/chemenu/commands/dist_cmd.py
- tools/chemenu/commands/docs_verify.py
- tools/chemenu/commands/doctor.py
- tools/chemenu/commands/git_publish.py
- tools/chemenu/commands/upstream_cmd.py
- tools/chemenu/commands/work_cmd.py
- tools/chemenu/config.py
- tools/chemenu/ownership.py
- tools/chemenu/tests/test_cli.py
- tools/chemenu/tests/test_dist_cmd.py
- tools/chemenu/tests/test_instructions_shell.py
- tools/chemenu/tests/test_preflight.py
- tools/chemenu/tests/test_preflight_pwsh.py
- tools/chemenu/tests/test_run_budget.py
- tools/chemenu/tests/test_upstream_cmd.py
- tools/chemenu/toc.py
- tools/preflight.ps1
- tools/preflight.sh

tools/README.md

@@ -71,7 +71,7 @@ tools/
   wikitool                 entry point (POSIX sh): stops with exit 42 until the preflight has passed
   wikitool.ps1             the same entry point for PowerShell 7, which resolves `tools/wikitool` to this file first
   run_wikitool.py          what the launcher runs with the venv's Python - puts chemenu on sys.path without PYTHONPATH, sets stdout/stderr to UTF-8
-  preflight.sh             checks prerequisites.txt, records .wikitool-tools.json, creates .venv (POSIX sh); as the release asset, downloads and unpacks the stack first
+  preflight.sh             checks prerequisites.txt, records .wikitool-tools.json, creates .venv (POSIX sh); as the release asset, downloads the stack and unpacks it into its own (empty) folder first
   preflight.ps1            the same for PowerShell 7; also checks the execution policy and the Mark of the Web
   prerequisites.txt        what the machine needs, one `|`-separated line per tool - read by the preflight and `doctor`
   trace-hook               what the harness hooks call: trace_ingest.py under the venv's Python
@@ -91,7 +91,7 @@ tools/
     links.py               labelled edges in `related:` - the graph's semantics as data, not prose
     kb_collections.py      collection discovery (a directory with COLLECTION.md), and what one declares about itself
     conventions.py         kb/CONVENTIONS.md: what this instance decided about authoring, as opposed to what the stack enforces
-    ownership.py           the stack-vs-instance boundary under a content stage - one predicate, read by `dist_cmd.py` and `commands/upstream_cmd.py` so the two cannot answer it differently
+    ownership.py           the stack-vs-instance boundary under a content stage - one predicate, so no caller keeps a list of its own
     type_resolver.py       type-spec loading and schema resolution
     catalog.py             how the corpus groups into collections and areas, and the shard threshold - with no CLI attached
     lint_core.py           the lint checks and the report, with no CLI attached