fix: Help text: mention --gcov alias in Automation section (fixes #1213) (#1214)

Summary
- Update help text to mention `--gcov` alias alongside
`--discover-and-gcov` for consistency with README and parser.
- Align error suggestions to prefer `--gcov` (alias) and remove
misleading gcov path suggestion; advise ensuring `gcov` on `PATH`.

Scope
- src/config/help/config_help_core.f90
- src/core/error/error_handlers.f90
- No behavior changes.

Verification
- Build and test:
  - Command: fpm test
    Output excerpt:
      Project compiled successfully.
      OK: cli flags rejection minimal
- Help text:
  - Command: fpm run -- --help | sed -n '1,40p'
    Output excerpt includes:
      "Use --gcov (alias: --discover-and-gcov)"
      Automation section shows `--gcov` and alias line.

Rationale
- Keep user-facing messages consistent across help and error
suggestions. Remove stale guidance implying `--gcov` accepts a path
value, which is no longer supported.

Author: krystophny

src/config/help/config_help_core.f90

@@ -20,7 +20,7 @@ subroutine show_help_information()
         print '(A)', "Usage: fortcov [OPTIONS] [COVERAGE_FILES...]"
         print '(A)', ""
         print '(A)', "Note: FortCov analyzes existing .gcov files by default."
-        print '(A)', "      Use --discover-and-gcov to auto-discover builds and run gcov."
+        print '(A)', "      Use --gcov (alias: --discover-and-gcov) to auto-discover builds and run gcov."
         print '(A)', ""
         print '(A)', "Options:"
         print '(A)', "  -h, --help                Show this help and exit"
@@ -39,11 +39,12 @@ subroutine show_help_information()
         print '(A)', "  --fail-under PERCENT      Exit non-zero if coverage below PERCENT"
         print '(A)', ""
         print '(A)', "Automation:"
-        print '(A)', "  --discover-and-gcov       Auto-discover builds and run gcov before analysis"
+        print '(A)', "  --gcov                    Auto-discover builds and run gcov before analysis"
+        print '(A)', "                             (alias: --discover-and-gcov)"
         print '(A)', ""
         print '(A)', "Examples:"
         print '(A)', "  fortcov --source=src *.gcov --output=report.md"
-        print '(A)', "  fortcov --discover-and-gcov --fail-under 80"
+        print '(A)', "  fortcov --gcov --fail-under 80"
         print '(A)', ""
         print '(A)', "For more information, visit: https://github.com/lazy-fortran/fortcov"
 

src/core/error/error_handlers.f90

@@ -109,7 +109,7 @@ subroutine handle_invalid_config(config_file, line_number, error_ctx)
         error_ctx%suggestion = trim(error_ctx%suggestion) // char(10) // &
             "2. Example: fortcov --source=src *.gcov --output=coverage.md"
         error_ctx%suggestion = trim(error_ctx%suggestion) // char(10) // &
-            "3. For auto mode: fortcov --discover-and-gcov"
+            "3. For auto mode: fortcov --gcov (alias: --discover-and-gcov)"
 
         write(error_ctx%context, '(A)') "Configuration parsing"
     end subroutine handle_invalid_config
@@ -196,7 +196,7 @@ subroutine handle_gcov_not_found(gcov_path, error_ctx)
         error_ctx%suggestion = trim(error_ctx%suggestion) // char(10) // &
             "2. Find gcov location: which gcov || find /usr -name 'gcov*'"
         error_ctx%suggestion = trim(error_ctx%suggestion) // char(10) // &
-            "3. Specify path: --gcov=/usr/bin/gcov-11"
+            "3. Ensure gcov is on PATH (e.g., gcov-11)"
         error_ctx%suggestion = trim(error_ctx%suggestion) // char(10) // &
             "4. Check gcc installation: gcc --version"