fix(mux): delete server.lock before starting server (#591)

## Summary

Remove stale `~/.mux/server.lock` file before starting the mux server to
prevent startup failures when a previous server didn't clean up
properly.

## Changes

- Added `rm -f "${HOME}/.mux/server.lock"` at the start of the `run_mux`
function
- Bumped version to 1.0.5

## Testing

- All Terraform tests pass
- Shellcheck passes with only style warnings (unrelated to this change)

---------

Co-authored-by: Atif Ali <atif@coder.com>

registry/coder/modules/mux/README.md

@@ -14,7 +14,7 @@ Automatically install and run [mux](https://github.com/coder/mux) in a Coder wor
 module "mux" {
   count    = data.coder_workspace.me.start_count
   source   = "registry.coder.com/coder/mux/coder"
-  version  = "1.0.4"
+  version  = "1.0.5"
   agent_id = coder_agent.main.id
 }
 ```
@@ -37,7 +37,7 @@ module "mux" {
 module "mux" {
   count    = data.coder_workspace.me.start_count
   source   = "registry.coder.com/coder/mux/coder"
-  version  = "1.0.4"
+  version  = "1.0.5"
   agent_id = coder_agent.main.id
 }
 ```
@@ -48,7 +48,7 @@ module "mux" {
 module "mux" {
   count    = data.coder_workspace.me.start_count
   source   = "registry.coder.com/coder/mux/coder"
-  version  = "1.0.4"
+  version  = "1.0.5"
   agent_id = coder_agent.main.id
   # Default is "latest"; set to a specific version to pin
   install_version = "0.4.0"
@@ -61,7 +61,7 @@ module "mux" {
 module "mux" {
   count    = data.coder_workspace.me.start_count
   source   = "registry.coder.com/coder/mux/coder"
-  version  = "1.0.4"
+  version  = "1.0.5"
   agent_id = coder_agent.main.id
   port     = 8080
 }
@@ -75,7 +75,7 @@ Run an existing copy of mux if found, otherwise install from npm:
 module "mux" {
   count      = data.coder_workspace.me.start_count
   source     = "registry.coder.com/coder/mux/coder"
-  version    = "1.0.3"
+  version    = "1.0.5"
   agent_id   = coder_agent.main.id
   use_cached = true
 }
@@ -89,7 +89,7 @@ Run without installing from the network (requires mux to be pre-installed):
 module "mux" {
   count    = data.coder_workspace.me.start_count
   source   = "registry.coder.com/coder/mux/coder"
-  version  = "1.0.4"
+  version  = "1.0.5"
   agent_id = coder_agent.main.id
   install  = false
 }

registry/coder/modules/mux/run.sh

@@ -5,6 +5,9 @@ RESET='\033[0m'
 MUX_BINARY="${INSTALL_PREFIX}/mux"
 
 function run_mux() {
+  # Remove stale server lock if present
+  rm -f "$HOME/.mux/server.lock"
+
   local port_value
   port_value="${PORT}"
   if [ -z "$port_value" ]; then