[Bug]: Routes server -- Revit fatal crash on first HTTP request after pyRevit Reload

[kimust]

✈ Pre-Flight checks

• I don't have SentinelOne antivirus installed (see above for the solution)
• I have searched in the issues (open and closed) but couldn't find a similar issue
• I have searched in the pyRevit Forum for similar issues
• I already followed the installation troubleshooting guide thoroughly
• I am using the latest pyRevit Version

🐞 Describe the bug

I'm a BIM engineer doing construction design (shop drawings) for HVAC systems, building a small local HTML dashboard that talks to a running Revit session
through the Routes API (just a few read-only GET routes - element counts, view lists). Everything worked fine until I started using pyRevit Reload during
development.

What happens: if the Routes server is enabled and I press pyRevit Reload, the next
HTTP request I send (any route, even a trivial ping that returns doc.Title) crashes
Revit completely - error report dialog, process gone. This happens every single time.
I got the same crash journal signature in two separate sessions.

Some things I checked before reporting:

• Requests before any Reload work fine, repeatedly (~350-400ms each). It's only
  after a Reload that the first request kills Revit.
• I first suspected the old server thread surviving the reload, so I enabled file
  logging. Turns out the reload actually swaps the server cleanly - the log shows
  the old one stopping without errors and "Routes server is listening on
  http://0.0.0.0:48884" at the end of the reload. And the very next request still
  crashes Revit. So the freshly recreated server is the broken one, not a leftover.
• Hooks (doc-saved) that get re-registered by the same Reload keep working fine
  afterwards. So Reload itself seems ok - it looks specific to the routes request
  handler (the ExternalEvent) being re-created during a Reload.

⌨ Error/Debug Message

Revit journal, last lines before the process dies (same in both crashes):

  ' [Jrn.ExternalEventExecution] Rvt.Attr.AddInId: b39107c3-a1d7-47f4-a5a1-532ddf6edb5d
    Rvt.Attr.AddInName: PyRevitLoader Rvt.Attr.AddInVersion: 2.7.12.0
    Rvt.Attr.ExternalEventName: RequestHandler Rvt.Attr.VendorId: eirannejad
  ' 0:< Exception occurred
  'C ... ExceptionCode=0xe0434352 ExceptionFlags=0x00000001 ExceptionAddress=00007FFA9DE65369
  ...
  ' 0:< unhandledExceptionFilter is executed in a non-main thread

  pyRevit runtime log during the reload right before the crash (server swap itself looks fine):
  INFO [<Reload> pyrevit.loader.sessionmgr] Routes server is listening on http://0.0.0.0:48884
  I still have both full CER packages (journal + minidump) if needed.

♻️ To Reproduce

1. Enable the routes server, start Revit 2025, open any project (a plain sample model reproduces it)
2. Register any simple GET route from an extension startup.py (mine just returns doc.Title)
3. Send a GET to the route - works fine, as many times as you want
4. Press pyRevit Reload, let it finish
5. Send one more GET to any route
6. Revit crashes fatally. Every time.

⏲️ Expected behavior

The request after a reload should just get served (or at worst return an HTTP 500).
A broken route handler shouldn't take down the whole Revit process with an unhandled
exception on a background thread.

🖥️ Hardware and Software Setup (please complete the following information)

pyRevit 6.5.2.26175+2113 (master, deployed from image)
  Engine: DEFAULT (IronPython 2712), Active CPython: 3123
  Revit 2025.4.5 Update (build 20260410_1515 x64)
  Windows 10 (10.0.19045), per-user install, no admin
  pyRevit CLI v6.5.2.26175+2113.04a9b197d2e8d895852d8e693a4223b2dbe78075
  Routes: enabled = true, default port 48884

Additional context

Workaround I'm running now, verified across multiple reloads + many requests (before the patch: first request after reload crashed 100%, twice):
In pyrevitlib/pyrevit/routes/server/init.py I stopped init() from touching the
running server on reload, so the server created at Revit startup just keeps serving:

def init():
    router.reset_routes()
    # removed: deactivate_server()

def activate_server():
    routes_server = envvars.get_pyrevit_env_var(envvars.ROUTES_SERVER)
    if routes_server:
        return routes_server   # also silences the false "Routes servers failed activation" error
    ...

Trade-off is that route code changes now need a Revit restart instead of a reload,
so this is a mitigation, not a fix.

Small side note: deactivate_server() might want a try/finally so a failed stop()
can't strand the env var registration.

Is there a known reason an ExternalEvent + IronPython handler created during a
reload would blow up like this on first execution, while the one created at Revit
startup is fine? Happy to provide the dumps or open a PR if that helps.