preview: update consumers for shared FCS and PDF changes

[Austin-s-h]

Summary

Update consumer lambdas to use the new shared FCS parsing layer from #4858, plus PDF preview refactor sharing the same lambda base.

Affected lambdas

• lambdas/indexer/ — index FCS metadata
• lambdas/preview/ — render FCS preview with new vegaLite field
• lambdas/tabular_preview/ — minor adjustments
• lambdas/thumbnail/ — PDF refactor + FCS-aware thumbnails

Stack relationship

This PR is stacked on top of #4858 (rebase-based). Until #4858 lands on master, this PR's diff against master will include the shared-layer changes from #4858; review the diff in that lens, or review #4858 first.

PR	Layer
#4858	Shared lambda parsing + vegaLite spec
#4859 (this)	Consumer lambdas updated to use shared layer
#4860	Catalog frontend Vega chart rendering

Validation

• cd lambdas/<consumer> && uv run pytest
• End-to-end FCS file preview smoke (deployment-side)

Deployment context

Tracked in deployment#2395; rolled out via deployment#2394.

[codecov]

Codecov Report

❌ Patch coverage is 99.43820% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 45.95%. Comparing base (cea497e) to head (d789f0b).

Files with missing lines	Patch %	Lines
lambdas/thumbnail/tests/test_thumbnail.py	94.44%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4859      +/-   ##
==========================================
+ Coverage   45.69%   45.95%   +0.25%     
==========================================
  Files         829      830       +1     
  Lines       33532    33694     +162     
  Branches     5698     5698              
==========================================
+ Hits        15323    15484     +161     
- Misses      16212    16213       +1     
  Partials     1997     1997              

Flag	Coverage Δ
api-python	93.14% <ø> (ø)
catalog	19.55% <ø> (ø)
lambda	96.79% <99.43%> (+0.16%)	⬆️
py-shared	98.18% <ø> (ø)

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[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[drernie]

@Austin-s-h heads-up — your consumer-update branch has been rebased on top of #4858 so it inherits all the latest shared-layer fixes (Greptile P1+P2, Copilot's empty-token / numpy.isfinite / memory refactor / py-shared cleanup).

What changed on austin/preview-lambda-consumers

• Rebased onto austin/preview-lambda-shared (instead of plain master). Your single consumer commit e9463158 is now on top of the post-fix shared-layer state.
• No content changes to the consumer lambdas themselves — just rebase.

Stack relationship
This PR is now stacked on #4858. Until #4858 lands on master, this PR's diff against master will include the shared-layer changes from #4858; review the diff in that lens, or review #4858 first.

Status

• CI: ✅ all 44 checks green
• Copilot review errored twice (Copilot-side issue, not your code) — could retry manually via the GitHub UI
• Mergeable, awaiting human review

(Note: Copilot reviewed #4858 successfully but errored on this one and on #4860 — appears to be flaky on GitHub's side, not anything wrong with the PRs.)