feat(sheets): add read-format command and borders guardrails

[nilzzzzzz]

Description

Hi @steipete,

follow-up to #72.
This PR adds Sheets format readback and tightens formatting safety around border typos.

Also includes a tiny contacts compile fix (2 signature type corrections) to unblock CI/build on current main.

What this PR changes

• Adds gog sheets read-format (aliases: get-format, format-read).
• Adds --effective mode for read-format.
• Hardens gog sheets format input validation for boarders typo and unknown JSON keys.
• Adds tests, docs, changelog updates.
• Fixes contacts helper arg types to make go build / CI pass.

Command behavior (clear contract)

gog sheets read-format <spreadsheetId> <range>

• Reads user-entered cell format (userEnteredFormat) for every formatted cell in range.
• JSON output fields:
  • spreadsheetId
  • range
  • source (userEnteredFormat)
  • formats[] with sheet, a1, row, col, value, format
• Text output:
  • table columns: A1, VALUE, FORMAT (format serialized as JSON)

gog sheets read-format <spreadsheetId> <range> --effective

• Reads effective computed format (effectiveFormat) instead of user-entered format.
• Useful to verify final rendered format after defaults/theme/rules.

gog sheets format ... --format-json ... --format-fields ... (existing command improved)

• --format-json now uses strict decode (DisallowUnknownFields) so unknown keys fail early.
• --format-fields now detects boarders typo and returns explicit guidance to use borders.

Why the contacts fix is in this PR

Current main has a compile break in internal/cmd/contacts_crud.go due mismatched helper argument types.
Without fixing that, CI fails before Sheets tests run.
This PR applies the minimal 2-line signature correction only to unblock build.

Prompt history (verbatim-ish)

• "We have the format command for sheets but not a way to read it... put the read format value ... and check the boarders"
• "install it also and update my skil"
• "did we add tests like in the other pr?"
• "...test to format this nicely"
• "mention it also that we did this to unblock ci. Explain better what really the different commands we implemnted do in the pr, make it less sloppy"

How has this been tested?

• go build ./cmd/gog
• go test ./internal/cmd -run 'TestSheetsReadFormatCmd|TestSheetsFormatCmd_BordersTopStyle|TestApplyForceSendFields_BordersTopStyle|TestHasBoardersTypo|TestSheetsFormat_ValidationErrors|TestExecute_SheetsMoreCommands|TestContacts(Create|Update)' -count=1
• Manual live test on provided sheet/tab:
  • spreadsheet: 1T2R_IXqmrSz1rGOj1ERq7U7TM2v3wZ_2rOsgcYA8jAQ
  • tab (gid=1911010233): Original Plan
  • applied header/body/border/number formatting
  • verified via gog sheets read-format ... --json

[steipete]

Landed after manual rebase/conflict resolution onto main.

• Gate: go test ./internal/cmd -run 'TestSheets(ReadFormatCmd|FormatCmd_BordersTopStyle|ApplyForceSendFields_BordersTopStyle|HasBoardersTypo|Execute_SheetsMoreCommands)' -count=1; make ci
• Land commit: 57ff818
• Merge commit: 79546b9

Thanks @nilzzzzzz!