Return add command errors rather than log + swallowing them

[bhq12]

Fix #28

Replicated issue before the fix against google.com:

Confirmed after re-building that semantifly works as expected against bing.com

Confirmed postgres index table contains the complete bing metadata (with the bad google.com entry from pre-fix commands):

Subcommand tests still passing after change (note I had to update the echo.jsontest.com calls in the tests to api.github.com instead as I was having DNS issues with echo.jsontest.com, unsure if this is a my-network thing though so haven't included that change in the PR):

go test . -v
=== RUN   TestAdd
--- Testing Add command ---
--- PASS: TestAdd (0.03s)
=== RUN   TestAdd_MultipleFilesSamePath
--- PASS: TestAdd_MultipleFilesSamePath (0.01s)
=== RUN   TestAdd_Webpage
--- PASS: TestAdd_Webpage (2.41s)
=== RUN   TestAdd_Database
--- PASS: TestAdd_Database (0.01s)
=== RUN   TestDelete
--- Testing Delete command ---
--- PASS: TestDelete (0.01s)
=== RUN   TestGet
--- Testing Get command ---
--- PASS: TestGet (0.01s)
=== RUN   TestGet_Webpage
--- PASS: TestGet_Webpage (1.14s)
=== RUN   TestGet_Database
--- PASS: TestGet_Database (1.24s)
=== RUN   TestLexicalSearch
--- Testing LexicalSearch command ---
=== RUN   TestLexicalSearch/Search_for_'test'
=== RUN   TestLexicalSearch/Search_for_'search'
=== RUN   TestLexicalSearch/Search_for_non-existent_term
--- PASS: TestLexicalSearch (0.00s)
    --- PASS: TestLexicalSearch/Search_for_'test' (0.00s)
    --- PASS: TestLexicalSearch/Search_for_'search' (0.00s)
    --- PASS: TestLexicalSearch/Search_for_non-existent_term (0.00s)
=== RUN   TestLexicalSearch_NonExistentIndex
--- PASS: TestLexicalSearch_NonExistentIndex (0.00s)
=== RUN   TestLexicalSearch_UnexpectedTopN
--- PASS: TestLexicalSearch_UnexpectedTopN (0.00s)
=== RUN   TestPrintSearchResults
--- PASS: TestPrintSearchResults (0.00s)
=== RUN   TestParseArgs
=== RUN   TestParseArgs/Simple_flag_and_non-flag_arguments
=== RUN   TestParseArgs/Flags_with_equal_sign
=== RUN   TestParseArgs/Boolean_flag
=== RUN   TestParseArgs/Boolean_flag_v2
=== RUN   TestParseArgs/Complicated_bool_flags
=== RUN   TestParseArgs/Multiple_flags_and_non-flag_arguments
=== RUN   TestParseArgs/No_flags,_only_non-flag_arguments
=== RUN   TestParseArgs/Only_flags,_no_non-flag_arguments
=== RUN   TestParseArgs/Complicated_test:_different_types_of_flags_and_order_of_arguments
=== RUN   TestParseArgs/No_args
--- PASS: TestParseArgs (0.00s)
    --- PASS: TestParseArgs/Simple_flag_and_non-flag_arguments (0.00s)
    --- PASS: TestParseArgs/Flags_with_equal_sign (0.00s)
    --- PASS: TestParseArgs/Boolean_flag (0.00s)
    --- PASS: TestParseArgs/Boolean_flag_v2 (0.00s)
    --- PASS: TestParseArgs/Complicated_bool_flags (0.00s)
    --- PASS: TestParseArgs/Multiple_flags_and_non-flag_arguments (0.00s)
    --- PASS: TestParseArgs/No_flags,_only_non-flag_arguments (0.00s)
    --- PASS: TestParseArgs/Only_flags,_no_non-flag_arguments (0.00s)
    --- PASS: TestParseArgs/Complicated_test:_different_types_of_flags_and_order_of_arguments (0.00s)
    --- PASS: TestParseArgs/No_args (0.00s)
=== RUN   TestServerCommands
2025/07/16 17:53:15 server listening at [::]:50051
2025/07/16 17:53:15 using index path: ./test_semantifly
--- PASS: TestServerCommands (0.12s)
=== RUN   TestHelpFlag
=== RUN   TestHelpFlag/--help
=== RUN   TestHelpFlag/-h
--- PASS: TestHelpFlag (0.02s)
    --- PASS: TestHelpFlag/--help (0.01s)
    --- PASS: TestHelpFlag/-h (0.01s)
=== RUN   TestAddSubcommand
=== RUN   TestAddSubcommand/Help
=== RUN   TestAddSubcommand/Non-existing_file
=== RUN   TestAddSubcommand/Bad_flag
=== RUN   TestAddSubcommand/Existing_file
=== RUN   TestAddSubcommand/Creates_new_directory_for_index
--- PASS: TestAddSubcommand (0.05s)
    --- PASS: TestAddSubcommand/Help (0.01s)
    --- PASS: TestAddSubcommand/Non-existing_file (0.01s)
    --- PASS: TestAddSubcommand/Bad_flag (0.01s)
    --- PASS: TestAddSubcommand/Existing_file (0.01s)
    --- PASS: TestAddSubcommand/Creates_new_directory_for_index (0.01s)
=== RUN   TestGetSubcommand
=== RUN   TestGetSubcommand/Get_existing_file
=== RUN   TestGetSubcommand/Get_after_delete
=== RUN   TestGetSubcommand/Get_bad_index_file
--- PASS: TestGetSubcommand (0.05s)
    --- PASS: TestGetSubcommand/Get_existing_file (0.01s)
    --- PASS: TestGetSubcommand/Get_after_delete (0.02s)
    --- PASS: TestGetSubcommand/Get_bad_index_file (0.02s)
=== RUN   TestUpdateSubcommand
=== RUN   TestUpdateSubcommand/Update_without_URI
=== RUN   TestUpdateSubcommand/Update_with_new_file
--- PASS: TestUpdateSubcommand (0.03s)
    --- PASS: TestUpdateSubcommand/Update_without_URI (0.01s)
    --- PASS: TestUpdateSubcommand/Update_with_new_file (0.01s)
=== RUN   TestDeleteSubcommand
=== RUN   TestDeleteSubcommand/Delete_bad_index_file
=== RUN   TestDeleteSubcommand/Delete_existing_file
=== RUN   TestDeleteSubcommand/Delete_from_empty_index
--- PASS: TestDeleteSubcommand (0.04s)
    --- PASS: TestDeleteSubcommand/Delete_bad_index_file (0.01s)
    --- PASS: TestDeleteSubcommand/Delete_existing_file (0.01s)
    --- PASS: TestDeleteSubcommand/Delete_from_empty_index (0.01s)
=== RUN   TestWebpageOperations
=== RUN   TestWebpageOperations/Add_webpage
=== RUN   TestWebpageOperations/Get_webpage
=== RUN   TestWebpageOperations/Update_webpage
=== RUN   TestWebpageOperations/Get_webpage#01
=== RUN   TestWebpageOperations/Delete_webpage
--- PASS: TestWebpageOperations (7.38s)
    --- PASS: TestWebpageOperations/Add_webpage (2.17s)
    --- PASS: TestWebpageOperations/Get_webpage (1.71s)
    --- PASS: TestWebpageOperations/Update_webpage (1.51s)
    --- PASS: TestWebpageOperations/Get_webpage#01 (1.98s)
    --- PASS: TestWebpageOperations/Delete_webpage (0.01s)
=== RUN   TestUpdate
--- Testing Update command ---
--- PASS: TestUpdate (0.01s)
=== RUN   TestUpdate_Database
--- PASS: TestUpdate_Database (0.01s)
PASS
ok      accretional.com/semantifly/subcommands  25.836s