Clarify TC donation, stability review timeline and expectations

[jack-berg]

During the 1/21/26 TC meeting, we discussed TC review expectations for both donation proposals and stability reviews, and agreed that it would be useful to clarify a few points:

• For both donations and stability reviews, timelines vary, but the TC should generally aim to provide feedback within a month after assignment. If not practical for any reasons (e.g. complexity, competing priorities) the TC member should begin providing regular updates on the respective issue.
• For both donations and stability reviews, clarify expectations the expectation of a dialogue, where both the TC member and donating org / requesting maintainer are expected to be engaged / responsive.

To make these clarifications, this PR:

• Adds a new entry in processes.md defining the TC stability review process. This is currently implicit - making it explicit gives us a place to write about it. Include guidance on timelines.
• Link to the TC stability review process in the tech-commitee-charter.md document as a part of the responsibilities section
• Extends the stabilization review template with a checkbox for the maintainer to indicate they understand the dialogue aspect of the TC review process
• Update donations.md file to include guidance on timelines, and clarify the expectation that the donating org is responsive through the process.

cc @open-telemetry/technical-committee

[jsuereth]

Thanks for adding this clarification!

The response time and caveats all look great to me.

[jack-berg]

Should be good to merge this @open-telemetry/governance-committee