fix(nushell): improve robustness and clarify abstraction boundaries

- pj_completions: merge into $env.config instead of replacing it wholesale
- pj_completions: use parse-time const for cache dir instead of pwd fallback
- pj_fzf / pj_historyhintcomplete: null-safe keybindings access via ? and default
- pj_helix: replace $env.OS (Windows-only) with $nu.os-info.name; extract shared launcher
- pj_prompt: fix off-by-one in git OID substring (0..7 -> 0..<7)
- pj_prompt: use $nu.os-info.name for OS detection instead of sys host hostname
- pj_prompt: cache git availability in static base, skip per-render which call
- pj_prompt: bind LAST_EXIT_CODE once in right-prompt closure
- pj_brew / pj_uv: add --ignore-errors to hide-env calls
- pj_aliases: convert quote/dadjoke to defs with try/catch error handling
- pj_deepseek: guard curl availability before invoking
- pj_zoxide: add ? to $nu.os-info.name access
- pj_starship: fix null-to-nuon producing "null" string; broaden detection
- nu_polyjuice: load pj_starship module

nushell/modules/pj_prompt.nu

@@ -1,9 +1,9 @@
 def _pj_detect_os_key [] {
-    let host_name = (((sys host | get name?) | default ($nu.os-info.name? | default "")) | into string | str lowercase)
-    if ($host_name | str contains "darwin") {
+    let os_name = ($nu.os-info.name? | default "" | into string | str lowercase)
+    if ($os_name | str contains "darwin") {
         return "Macos"
     }
-    if ($host_name | str contains "windows") {
+    if ($os_name | str contains "windows") {
         return "Windows"
     }
 
@@ -53,7 +53,7 @@ def _pj_detect_os_key [] {
             _ => "Linux"
         }
     } else {
-        if ($host_name | str contains "linux") {
+        if ($os_name | str contains "linux") {
             "Linux"
         } else {
             "Unknown"
@@ -211,8 +211,8 @@ def _pj_is_path_within [path: string, base: string] {
 
 # Single `git rev-parse` call: returns whether we are inside a work tree and the
 # normalized repo root (empty string when not in a repo).
-def _pj_git_repo_info [] {
-    if (which ^git | is-empty) {
+def _pj_git_repo_info [has_git: bool] {
+    if not $has_git {
         return { inside: false, root: "" }
     }
 
@@ -378,7 +378,7 @@ def _pj_git_info [repo: record] {
         } else {
             ($oid_line | str replace "# branch.oid " "" | str trim)
         }
-        ($oid | str substring 0..7)
+        ($oid | str substring 0..<7)
     } else {
         $head_name
     }
@@ -587,6 +587,7 @@ def _pj_prompt_static_base [] {
     let in_ssh = (($env.SSH_CONNECTION? | default "") != "" or ($env.SSH_TTY? | default "") != "")
     # let prompt_newline = if (($nu.os-info.name | str lowercase) == "windows") { "\n\r" } else { "\n\r" }
     let prompt_newline = "\n\r"
+    let has_git = (which ^git | is-not-empty)
 
     {
         os_symbol: (_pj_os_symbol)
@@ -595,6 +596,7 @@ def _pj_prompt_static_base [] {
         in_ssh: $in_ssh
         shell_name: "nu"
         prompt_newline: $prompt_newline
+        has_git: $has_git
     }
 }
 
@@ -611,7 +613,7 @@ def _pj_left_prompt [] {
     }
 
     let shell_part = $"($p.c_shell) ($static.shell_name) ($p.c_reset)"
-    let repo = (_pj_git_repo_info)
+    let repo = (_pj_git_repo_info $static.has_git)
     let dir = (_pj_truncate_pwd $env.PWD 4 $repo)
     let git = (_pj_git_info $repo)
     let git_part = (_pj_git_branch_module $p $git)
@@ -681,8 +683,9 @@ export-env {
         }
         PROMPT_COMMAND_RIGHT: {||
             let p = ($env.PJ_PROMPT_PALETTE? | default (_pj_palette_default))
-            if (($env.LAST_EXIT_CODE? | default 0) != 0) {
-                $"($p.c_right_error)Exit code: ($env.LAST_EXIT_CODE)($p.c_reset)"
+            let exit_code = ($env.LAST_EXIT_CODE? | default 0)
+            if ($exit_code != 0) {
+                $"($p.c_right_error)Exit code: ($exit_code)($p.c_reset)"
             } else {
                 ""
             }