build a small python cli tool called `usajobs.py` for exploring usajobs results.

goal:
- query the official usajobs api
- apply strict local filters
- show results in a readable terminal table
- let me select rows to export into an org-mode file

stack:
- python 3.11+
- click for cli args
- requests for api
- rich for table + row selection prompt
- pathlib/json/csv stdlib only otherwise

env vars:
- USAJOBS_EMAIL
- USAJOBS_KEY

basic command:
`python jobs.py search --location "Washington, DC" --radius 25 --salary-min 150 --grade-min 15 --grade-max 15 --series 2210 --series 0340 --clearance 3 --clearance 4`

option behavior:
- --radius 25 means 25 miles
- --salary-min 150 means $150,000
- --grade-min/--grade-max filter locally against low/high grade
- --series may repeat; pass to api as semicolon list
- --clearance may repeat; pass to api as semicolon list
- --pay-plan may repeat, default gs and gg
- --limit defaults 100
- --out defaults jobs.org
- --cache-dir defaults .cache/usajobs

search behavior:
1. call https://data.usajobs.gov/api/search using official headers:
   host: data.usajobs.gov
   user-agent: $USAJOBS_EMAIL
   authorization-key: $USAJOBS_KEY
2. request fields=full, resultsperpage=500, sortfield=opendate, sortdirection=desc
3. cache raw json response per query/page under .cache/usajobs
4. apply local filters after fetching:
   - pay plan in allowed pay plans
   - low_grade >= grade_min
   - high_grade <= grade_max
   - salary max >= salary_min, or salary min >= salary_min if max absent
   - location string contains/near requested location as available
5. output table with columns:
   idx, title, agency, grade, salary, location, close date, clearance match, url
6. selection/export:
- after displaying table, allow user to arrow/highlight and mark for export
  - pick sensible defaults, eg x or m for mark, u for unmark, a for all, e for export
- export selected jobs to new file with short slug name + datetime stamp
- org output format:
```
** <shortened job title> [[url][link]]
:properties:
:agency: <agency>
:grade: <pay plan> <low>-<high>
:close_date: <date>
:end:

salary: <salary range>
location: <location>
travel: <travel percentage or unknown>
clearance: <clearance/security text or unknown>

*** posting
<raw posting text>
```
7. (stretch) Cache each query, allow arrow/scroll through them like a cli, recall, or save filters. could be too much.

implementation notes:
- write clean functional code:
  - build_params()
  - fetch_page()
  - fetch_all()
  - normalize_job()
  - passes_filters()
  - render_table()
  - parse_selection()
  - export_org()
- normalize both official api shape and frontend-ish shape if present:
  - api jobs may use MatchedObjectDescriptor
  - details may be under UserArea.Details
- raw posting text should combine title, summary, duties, requirements, qualifications, evaluations, other info, key requirements.
- shortened job title should be max 80 chars, strip all-caps screaming where reasonable, preserve meaning.
- include helpful errors if env vars missing.
- include a --offline flag that only reads cached json and does not call api.
- include a --debug flag that prints api params and counts before/after filtering.

acceptance test:
- running the command with `--salary-min 150 --grade-min 15 --grade-max 15 --radius 25` should not show gs/gg-13 jobs after local filtering.
- selecting `none` exits without writing.