fix(status): reset .Executed per prompt in cmd, bash and nushell

.Executed only turned false when the shell started, never again after
the first real command ran, so pressing enter on an empty line kept
the status segment visible. pwsh, zsh and fish already re-evaluate it
every prompt; bring clink, bash and nushell in line:

- clink: command_executed_mark now sets no_exit_code from the current
  input instead of only ever clearing it.
- bash: _omp_hook resets _omp_no_status=true before checking whether a
  command actually started, mirroring the zsh precmd hook.
- nushell: derive --no-status from whether history actually grew this
  prompt cycle instead of the one-shot CMD_DURATION_MS startup
  sentinel, which can't observe anything after the first command.

Fixes #7757

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018AhjcGCfxm2mFCfZhehLhv

Author: claude

src/shell/scripts/omp.bash

@@ -162,6 +162,7 @@ function _omp_hook() {
     _omp_job_count=${#_omp_jobs[@]}
 
     _omp_execution_time=-1
+    _omp_no_status=true
     if [[ $_omp_start_time ]]; then
         local omp_now=$(_omp_milliseconds)
         _omp_execution_time=$((omp_now - _omp_start_time))

src/shell/scripts/omp.lua

@@ -376,9 +376,7 @@ local function url_encode(str)
 end
 
 local function command_executed_mark(input)
-    if string.gsub(input, '^%s*(.-)%s*$', '%1') ~= '' then
-        no_exit_code = false
-    end
+    no_exit_code = string.gsub(input, '^%s*(.-)%s*$', '%1') == ''
 
     if not ftcs_marks_enabled then
         return

src/shell/scripts/omp.nu

@@ -35,13 +35,22 @@ def --wrapped _omp_get_prompt [
         $ms => { $ms | into int }
     }
 
+    # `$env.POSH_EXECUTED` is set once per prompt cycle in `$env.PROMPT_COMMAND`, based on
+    # whether history actually grew. Falls back to the execution-time sentinel when history
+    # is disabled, which only detects a freshly started shell.
+    let no_status = if $nu.history-enabled {
+        not ($env.POSH_EXECUTED? | default false)
+    } else {
+        $execution_time < 0
+    }
+
     (
         ^$_omp_executable print $type
             --save-cache
             --shell=nu
             $"--shell-version=($env.POSH_SHELL_VERSION)"
             $"--status=($env.LAST_EXIT_CODE)"
-            $"--no-status=($execution_time < 0)"
+            $"--no-status=($no_status)"
             $"--execution-time=($execution_time)"
             $"--terminal-width=((term size).columns)"
             $"--job-count=(job list | length)"
@@ -56,16 +65,24 @@ $env.PROMPT_MULTILINE_INDICATOR = (
 )
 
 $env.PROMPT_COMMAND = {||
+    let hist = if $nu.history-enabled { history } else { [] }
+    let hist_len = ($hist | length)
+
     # hack: sets cursor line to 1 on clear; not bulletproof, just a start
     let clear = $nu.history-enabled and (
-        (history | is-empty)
-        or (history | last | get command?) == "clear"
+        ($hist | is-empty)
+        or ($hist | last | get command?) == "clear"
     )
 
     if ($env.SET_POSHCONTEXT? | is-not-empty) {
         do --env $env.SET_POSHCONTEXT
     }
 
+    # a command was executed this prompt cycle only if history actually grew;
+    # an empty Enter (or history disabled) leaves the length unchanged
+    $env.POSH_EXECUTED = ($nu.history-enabled and ($hist_len > ($env.POSH_LAST_HISTORY_LEN? | default 0)))
+    $env.POSH_LAST_HISTORY_LEN = $hist_len
+
     _omp_get_prompt primary $"--cleared=($clear)"
 }