Fix path construction in configure_drivers directory iteration

[Copilot]

Dmod_ReadDir() returns entry names (e.g., "dmclk"), not full paths. When recursing into subdirectories like /configs/dmclk/, the code passed "dmclk" directly to VFS operations, causing lookups for /dmclk instead of /configs/dmclk.

Changes

• Construct absolute paths by joining config_path with entry names before passing to is_file(), read_driver_for_config(), and recursive calls
• Add separator handling (only insert / when config_path doesn't already end with one)
• Validate path length before construction to prevent overflow
• Fix error log to use config_path parameter instead of ctx->config_path

// Before: passes relative path
int res = configure_drivers(ctx, driver_name, entry);  // entry = "dmclk"

// After: constructs and passes absolute path
char full_path[MAX_PATH_LENGTH];
Dmod_SnPrintf(full_path, sizeof(full_path), "%s%s%s", 
              config_path,                    // "/configs"
              needs_separator ? "/" : "",     // "/"
              entry);                         // "dmclk"
int res = configure_drivers(ctx, driver_name, full_path);  // "/configs/dmclk"

Original prompt

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This section details on the original issue you should resolve

<issue_title>Niepoprawne iterowanie po katalogach w configure_drivers</issue_title>
<issue_description>W naszym scenariuszu mamy takie coś:

/ -> katalog root
/configs/ -> katalog z konfiguracjami przekazany do dmdevfs przy montowaniu
/configs/dmclk/ -> katalog z konfiguracjami dla drivera dmclk

I problem jest taki, że po tym jak dmdevfs znajdzie katalog configs, to w nim zaczyna szukac potem katalog /dmclk zamiast /configs/dmclk -> czyli uzywa sciezki wzglednej, zamiast bezwzglednej, przez co VFS zwraca informacje, ze takiego katalogu /dmclk nie ma i otrzymujemy komunikat:

[INFO] dmlist: Created list for module dmdevfs.
[INFO] Directory '/configs' opened successfully
dmdevfs: [ERROR] Failed to open config directory: /configs
dmdevfs: [ERROR] Failed to configure drivers in directory: dmclk

```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes Niepoprawne iterowanie po katalogach w configure_drivers #14

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