raw: fetch behind a login - raw login stores the user's session as a secret outside the tree, fetch.routes sends a host through it or to an external fetcher, a handler's render goes through the optional browser component (preflight --with browser) (#169); 10.0.0-beta.8

Files changed:
- CHANGES.md
- INSTALL.md
- VERSION
- docs/how-to/README.md
- docs/how-to/fetch-pages-behind-a-login.md
- docs/how-to/ingest-a-source.md
- docs/reference/commands/README.md
- docs/reference/commands/instance-health.md
- docs/reference/commands/raw-material-and-uploads.md
- docs/reference/configuration.md
- docs/reference/exit-codes.md
- instructions/preflight.md
- instructions/wiki-ingest/SKILL.md
- raw/CONTRACT.md
- sites/CONTRACT.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/browser.py
- tools/chemenu/cli_contract.py
- tools/chemenu/commands/doctor.py
- tools/chemenu/commands/raw/__init__.py
- tools/chemenu/commands/raw/fetch.py
- tools/chemenu/commands/raw/login.py
- tools/chemenu/config_shapes.py
- tools/chemenu/fetch_routes.py
- tools/chemenu/reference_doc.py
- tools/chemenu/settings.py
- tools/chemenu/sites/__init__.py
- tools/chemenu/sites/data.py
- tools/chemenu/sites/site.schema.json
- tools/chemenu/tests/test_cli.py
- tools/chemenu/tests/test_config_shapes.py
- tools/chemenu/tests/test_doctor.py
- tools/chemenu/tests/test_preflight.py
- tools/chemenu/tests/test_preflight_pwsh.py
- tools/chemenu/tests/test_raw_fetch_routes.py
- tools/chemenu/tests/test_raw_login.py
- tools/chemenu/tests/test_site_files.py
- tools/chemenu/web_capture.py
- tools/chemenu/web_session.py
- tools/preflight.ps1
- tools/preflight.sh
- tools/requirements-browser.txt

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SnAJ7Z3CpVD3PRbN73QtU2

instructions/preflight.md

@@ -24,6 +24,11 @@ Windows. The two answer the same questions from the same list and write the same
   `ABSENT` and is never a reason to stop, nor to install anything;
 - creates `tools/.venv` from the recorded Python and installs `tools/requirements.txt` into it.
 
+One more thing it does only when the user asks for it: `--with browser` installs the optional
+browser component - `tools/requirements-browser.txt` and the Chromium it drives - into
+`tools/.venv`. Only `raw login` and a page a site handler fetches through a browser need it. Once
+installed, every later run keeps it up to date; nothing else ever installs it.
+
 <!-- wikitool:toc -->
 ## Contents
 
@@ -148,6 +153,12 @@ It is safe to run at any time: a second run on a ready checkout changes nothing
 - **The venv or its libraries could not be installed.** The output carries the last lines of
   what Python or pip said. A network, proxy or security-product cause is for the user - or
   whoever administers their machine - to resolve; do not retry with other flags.
+- **A `wikitool` command names `--with browser`.** `raw login` or a rendered `raw fetch` needs the
+  optional browser component, and exits 42 saying so. Never pass `--with browser` yourself: it
+  downloads a browser onto the user's machine, which is the user's decision like any other
+  install. Show the output and wait; once the user has run it, a plain run of the preflight - yours
+  or theirs - keeps the component. A failure while installing it stops the preflight with exit 42
+  like any other, but leaves `.wikitool-tools.json` complete: every other command still runs.
 - **`.wikitool-tools.json` looks wrong.** Never edit it. Run the preflight again, with `--set` for
   a path the user names; `doctor` reports whether the result holds.