Document BSON value semantics and enforce strict docs

[quinnj]

The BSON docstring promises Dict-like mutation, but indexing an embedded document returns a decoded copy. Changing b["foo"]["bar"] leaves b unchanged, while assigning an existing key appends another field. Document these behaviors and execute a small dictionary-to-BSON rebuild example during the manual build.

The recipe is limited to ordinary decoded values supported by BSON's constructor. It states that dictionary conversion collapses duplicate keys and can lose binary subtype information; BSONTimestamp and BSONUnsupported require an explicit encoding. The example checks the nested result, original document, unrelated field, and unique field count.

Enable strict documentation checks after adding three missing type entries and fixing the existing BSONValue reference. Unchanged master fails those exact strict checks; the repaired complete manual passes. Package runtime code, dependencies, exports, versions, and workflows are unchanged.

Validation:

• Strict Documenter 0.27 builds pass on Linux Julia 1.6.7 and 1.13.0, including the executable example's five assertions and rendered tutorial/API checks.

• Sixteen public controls verify the nested-copy, array-copy, encoded-child snapshot, duplicate-key, and safe ordinary-value rebuild behavior on current source with both runtimes, and on the existing v0.9.0 source with Julia 1.13.0. These controls use native MongoC 1.30.8; the issue's historical Julia 1.9.3/native-driver combination was not recreated.

• Exact head d6da3368c6ac9939134203e7d0262d3baa3ab239 passes all 22 checks: both complete ten-job push/PR workflows and both coverage gates. All 18 expected uploads explicitly target Mongoc and that head; the public report is complete with 18 sessions at 83.77%.

• A private review of the complete source/documentation diff found no remaining blocker. This does not provide GitHub approval.

• Merged as 5d68e41a214ca1fbb0b0aff281b49d987d0ddab3; all ten main-branch jobs pass. All nine expected coverage uploads are accepted for that commit, with nine processed sessions at 84.14%. The tested and merged Git trees are identical.

• The published tutorial and API manual return HTTP 200 and include the corrected content. All 60 API source links point to the merge commit.

Relates to #113. The request for live nested mutation remains open; this change documents current behavior.

Co-authored by Codex

AI disclosure: This work was prepared with assistance from OpenAI Codex.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.14%. Comparing base (78508ac) to head (d6da336).
⚠️ Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #154      +/-   ##
==========================================
+ Coverage   84.01%   84.14%   +0.12%     
==========================================
  Files          11       11              
  Lines        1652     1652              
==========================================
+ Hits         1388     1390       +2     
+ Misses        264      262       -2     

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[quinnj]

Merged as 5d68e41a214ca1fbb0b0aff281b49d987d0ddab3. All ten main-branch jobs pass, and all nine expected coverage reports are accepted and processed for that commit (84.14%). The merge tree matches the tested tree.

The published tutorial and API manual return HTTP 200 with the corrected text; all 60 API source links name the merge commit. Issue #113 remains open for live nested mutation.

AI disclosure: This work was prepared with assistance from OpenAI Codex.