fix: projects/ directory should be gitignored — it is local installation config, not shared code (#561)

- Add projects/*.toml to .gitignore
- Remove existing TOML files from git tracking (git rm --cached)
- Add .toml.example templates with placeholder values
- Update BOOTSTRAP.md with new section on project TOML setup
- Update AGENTS.md directory layout description

Existing local installations are unaffected — gitignore only
prevents tracked files from being committed, local copies persist.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

projects/harb.toml.example

@@ -0,0 +1,26 @@
+# projects/harb.toml.example — Template for johba/harb
+#
+# Copy to projects/harb.toml and fill in box-specific values,
+# or run: disinto init https://codeberg.org/johba/harb
+
+name            = "harb"
+repo            = "johba/harb"
+repo_root       = "/home/YOU/harb"
+primary_branch  = "master"
+
+[ci]
+woodpecker_repo_id = 0
+stale_minutes      = 60
+
+[services]
+containers = ["ponder"]
+
+[matrix]
+room_id   = "!your_room_id:matrix.example.org"
+bot_user  = "@harb-factory:matrix.example.org"
+token_env = "MATRIX_TOKEN"
+
+[monitoring]
+check_prs            = true
+check_dev_agent      = true
+check_pipeline_stall = true