Feature: Show queue health stats with docket snapshot

[abrookins]

Adds a --stats option to docket snapshot that prints a table of stats at the end of the snapshot list. E.g.:

                                          Task Count Statistics by Function
┏━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━┳━━━━━━━━━┳━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
┃ Function                  ┃ Total ┃ Running ┃ Queued ┃                Oldest Queued ┃                Latest Queued ┃
┡━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━╇━━━━━━━━━╇━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┩
│ extract_memory_structure  │   511 │       9 │    502 │ at 2025-07-09 11:22:51 -0700 │ at 2025-07-09 11:24:14 -0700 │
│ extract_discrete_memories │    16 │       1 │     15 │ at 2025-07-09 11:22:51 -0700 │ at 2025-07-09 11:24:14 -0700 │
│ index_long_term_memories  │     1 │       0 │      1 │ at 2025-07-10 10:20:53 -0700 │ at 2025-07-10 10:20:53 -0700 │
└───────────────────────────┴───────┴─────────┴────────┴──────────────────────────────┴──────────────────────────────┘

[chrisguidry]

Love it!

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (977b99e) to head (6102107).

Additional details and impacted files

@@            Coverage Diff             @@
##              main      #147    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           28        28            
  Lines         3570      3675   +105     
  Branches       191       205    +14     
==========================================
+ Hits          3570      3675   +105     

Flag	Coverage Δ
python-3.12	100.00% <100.00%> (ø)
python-3.13	100.00% <100.00%> (ø)

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Files with missing lines	Coverage Δ
src/docket/cli.py	100.00% <100.00%> (ø)
tests/cli/test_snapshot.py	100.00% <100.00%> (ø)

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[chrisguidry]

Don't worry about that failing docs check, I need to debug that, looks great!