Fix #433: accept Classic delete --workbook Name syntax

[jacalata]

Closes #433.

Motivation

tabcmd Classic invokes delete as tabcmd delete --workbook "Name"
where --workbook carries the target name as its value. tabcmd 2
shipped tabcmd delete "Name" --workbook (name positional, flag as
type selector). This is a breaking CLI difference for anyone running
Classic scripts against tabcmd 2. Verified against Classic 2025.1 on
main-windows.tsi.lan.

Behavior change

For users: both forms now work.

• Positional name is now optional (nargs="?").
• --workbook/--datasource take an optional value (nargs="?").
  Bare form still means True (tabcmd 2 syntax); with a value, the
  value is the target name (Classic syntax).
• run_command resolves which form supplied the name and normalizes
  args.workbook/args.datasource to True.
• Mutual exclusion between --workbook and --datasource still holds.
• If a user passes both a positional and a flag value (e.g. tabcmd delete Name --workbook OtherName), the positional wins and the flag
  value is silently discarded. Not ideal; could be tightened to an
  explicit error in a follow-up.

Test plan

• tests/parsers/test_parser_delete.py — 11 tests covering: both
  forms, short flags (-w/-d), mutual exclusion, empty parse,
  positional+flag-value conflict, bare --workbook with no value,
  Classic form combined with -r project flag
• Full unit-test run: 340 passed, 2 skipped
• Verified live against Classic 2025.1 and tabcmd 2: published 3
  disposable workbooks, deleted via all three combinations (tabcmd 2
  form, tabcmd 2 with Classic-form flag, Classic 2025.1), same outcome
• run_command normalization not covered here; tracked in Test coverage gap: run_command logic in the recent parity sweep is untested #457

🤖 Generated with Claude Code

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
tabcmd
__main__.py	12	12	12	0%
_version.py	11	11	11	0%
tabcmd.py	15	15	15	0%
version.py	9	5	5	44%
tabcmd/commands
commands.py	10	10	10	0%
constants.py	77	18	18	77%
server.py	135	18	18	87%
tabcmd/commands/auth
session.py	394	50	50	87%
tabcmd/commands/datasources_and_workbooks
datasources_and_workbooks_command.py	157	18	18	89%
datasources_workbooks_views_url_parser.py	142	5	5	96%
delete_command.py	70	23	23	67%
export_command.py	120	25	25	79%
get_url_command.py	127	47	47	63%
publish_command.py	123	28	28	77%
runschedule_command.py	21	7	7	67%
tabcmd/commands/extracts
create_extracts_command.py	42	8	8	81%
decrypt_extracts_command.py	27	2	2	93%
delete_extracts_command.py	37	6	6	84%
encrypt_extracts_command.py	27	2	2	93%
extracts.py	20	2	2	90%
reencrypt_extracts_command.py	27	2	2	93%
refresh_extracts_command.py	48	10	10	79%
tabcmd/commands/group
create_group_command.py	29	5	5	83%
delete_group_command.py	27	2	2	93%
tabcmd/commands/project
create_project_command.py	46	8	8	83%
delete_project_command.py	35	4	4	89%
publish_samples_command.py	30	4	4	87%
tabcmd/commands/site
create_site_command.py	34	5	5	85%
delete_site_command.py	27	2	2	93%
edit_site_command.py	38	2	2	95%
list_command.py	77	12	12	84%
list_sites_command.py	29	2	2	93%
tabcmd/commands/user
add_users_command.py	29	5	5	83%
create_site_users.py	58	11	11	81%
create_users_command.py	59	9	9	85%
delete_site_users_command.py	43	5	5	88%
user_data.py	222	31	31	86%
tabcmd/execution
_version.py	2	2	2	0%
global_options.py	125	8	8	94%
localize.py	66	11	11	83%
logger_config.py	60	6	6	90%
tabcmd_controller.py	42	7	7	83%
TOTAL	2883	465	84%