[codex] Modernize README demos and progress ergonomics

[wolph]

Summary

• refresh the README with animated SVG demos and clearer usage examples for labels, totals, live output, and concurrent bars
• place the exact demo code directly under each animated SVG so the rendered output and source stay paired
• render README SVG colors from captured ANSI output so percentage/count colors match the library's real terminal gradient
• show the multiple-bar demo with independently progressing bars instead of synchronized values
• simplify the unknown-length demo to use a straightforward range loop
• remove the extra ergonomics SVG section, generated asset, and obsolete GPG release-verification section
• keep recent log lines visible in the hero SVG while the progress bar advances
• use branch-relative README SVG links so the PR branch renders its own demo assets
• add a repeatable README demo renderer plus tests so documented terminal output stays in sync
• add CLI rate limiting, tighten unit/progress formatting behavior, and harden stream/logging cleanup around failed bars
• isolate stream cleanup tests so stale redirected-output state does not leak between cases
• purge docs/superpowers files from the PR branch history

Validation

• python scripts/render_readme_demos.py --check
• .tox/py313/bin/python -m pytest tests/test_readme_demos.py -q --no-cov
• .tox/py313/bin/python -m pytest -q --no-cov
• .tox/py313/bin/pyright
• .tox/ruff/bin/ruff check scripts/render_readme_demos.py tests/test_readme_demos.py
• .tox/ruff/bin/ruff format --check scripts/render_readme_demos.py tests/test_readme_demos.py
• git diff --check

[gemini-code-assist]

Code Review

This pull request modernizes the progressbar2 library by introducing tqdm-style ergonomic options (such as desc, total, unit, unit_scale, and postfix), adding new Postfix and UnitProgress widgets, and improving print/log coexistence with a reversible logging stream wrapper. It also updates the CLI to support rate limiting and custom display flags, rewrites the README to be demo-led, and adds a script to generate SVG terminal demos. The review feedback identifies three key improvement opportunities: ensuring valid falsy values (like 0 or False) are not omitted in the Postfix widget, wrapping ProgressBarBase.finish in contextlib.suppress during error handling to prevent masking exceptions, and copying logger.handlers to a tuple during iteration to avoid concurrent modification errors.

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[gemini-code-assist]

If value is 0, 0.0, or False, not value evaluates to True, which causes the widget to return an empty string and omit these valid postfix values. Checking for None or empty collections/strings explicitly prevents this issue.

Suggested change

	value = data['variables'].get(self.name)
	if not value:
	return ''
	value = data['variables'].get(self.name)
	if value is None or (isinstance(value, (str, dict, list, set)) and not value):
	return ''

[gemini-code-assist]

If ProgressBarBase.finish(self) raises an exception during error handling, it will mask the original exception being raised. For robust error handling and consistency with the other cleanup calls, it should also be wrapped in contextlib.suppress(Exception).

Suggested change

	except Exception:
	with contextlib.suppress(Exception):
	StdRedirectMixin.finish(self, end='')
	with contextlib.suppress(Exception):
	ResizableMixin.finish(self)
	ProgressBarBase.finish(self)
	raise
	except Exception:
	with contextlib.suppress(Exception):
	StdRedirectMixin.finish(self, end='')
	with contextlib.suppress(Exception):
	ResizableMixin.finish(self)
	with contextlib.suppress(Exception):
	ProgressBarBase.finish(self)
	raise

[gemini-code-assist]

Iterating over logger_.handlers directly can raise a RuntimeError: list changed size during iteration if another thread adds or removes a handler concurrently. Iterating over a snapshot tuple(logger_.handlers) avoids this race condition.

Suggested change

	for logger_ in self._iter_loggers():
	for handler in logger_.handlers:
	for logger_ in self._iter_loggers():
	for handler in tuple(logger_.handlers):