delete the bug-report discord webhook, and the last dead HOME_DIR reads

DISCORD_BUG_REPORT_WEBHOOK is gone, with sendToDiscord and its helpers. Reports
still land in DATA_PATH/bug-reports — the disk write always happened first and
the webhook was only a ping about it, so nothing about the report is lost.

It was a personal notification channel living in deployment config, on a platform
whose owner is the only person who files reports. It was also never in
.env.example: the setup script wrote a variable nothing documented, which is the
same drift as PORT, in the other direction.

Note DISCORD_WEBHOOK_URL is a DIFFERENT variable — the notify sidecar's own
channel — and is untouched.

Then a parity sweep of setup / .env.example / what the code reads, which turned
up two leftovers from earlier today:

HOME_DIR was still read in six files, each with its own `?? homedir()` fallback.
Dead since nothing sets it, but a dead read is worse than none — it reads as a
supported override. They take homedir() directly now. user-instance.ts gets a
comment on why its line stays where it is: it sits above `process.env.HOME =
homeDir`, and homedir() reads $HOME, so a read moved below that assignment would
return whichever member was last spawned into. Two of the six had fallback chains
ending in process.cwd() and '' — the second would have silently disabled whatever
consumed it rather than failing.

VAULTWARDEN_URL was uncommented in .env.example among the variables setup writes,
though it is a plugin variable setup has never written. Commented out with the
other plugin entries.

The three files now agree: setup writes PORT, BROWSER_RELAY_PORT and
POSTGRES_URL; .env.example lists those plus JWT_SECRET and VAULT_STORE_KEY, which
are required by code and deliberately unwritten until the secret store lands.

Not typechecked (empty node_modules, frozen installs). Every changed file parses;
the setup section was run and writes three variables.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/servers/sidecar/claude/user-instance.ts

@@ -80,7 +80,9 @@ const OFFICER_AUTH_TOKEN = await sign({ id: dbUser.id, email, username: dbUser.u
 // perfect parity with terminal sessions (same config, credentials and transcript store,
 // interchangeable via `claude --resume`). That absence of isolation is precisely why `chat` is an
 // `execution` capability and can never be granted: this is a shell, not a feature flag.
-const homeDir = process.env.HOME_DIR ?? homedir();
+// Evaluated here, ABOVE the `process.env.HOME = homeDir` below: homedir() reads $HOME, so a
+// read placed after that assignment would return whatever was last spawned into.
+const homeDir = homedir();
 const globalToolsDir = join(DATA_PATH, 'tools');
 
 // The email_db MCP tool reads one account's SQLite store; match the API's choice (first enabled).