chore(repo): initial baseline import (docs v0.9.2 + bootstrap)

Imports the v0.9.2 documentation baseline and the bootstrap files
required by docs/governance/repository-bootstrap-plan.md v0.1.0 §3,
minus the justfile (added in the next commit).

This commit establishes the git history for the project. All previous
work lived only as filesystem state with no version control.

.editorconfig

@@ -0,0 +1,18 @@
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*.{rs,toml}]
+indent_size = 4
+
+[Makefile]
+indent_style = tab